Excitatory amino acid receptor modulators

ABSTRACT

Compounds of formula (I) in which R 1  is halo-C 1-10  alkyl; halo-C 2-10  alkenyl; or (CH 2 ) n Y in which n is 1 or 2 and Y is OH, CN, N 3 , OR 3 , SH, S(O) p R 4 , S(O) 3 H, NH 2 , NHR 5 , NR 6 R 7 , NHCOR 8 , NO 2 , CO 2 H, CONHR 9 , 1H-tetrazol-5-yl, 5-phenyltetrazol-2-yl or PO 3 H 2 ; R 3 , R 5 , R 6 , R 7 , R 8  and R 9  are each selected independently from C 1-4  alkyl, aryl and aryl-C 1-4  alkyl; R 4  is selected from C 1-4  alkyl, aryl, aryl-C 1-4  alkyl, and 1H-tetrazol-5-yl, carboxy-(1-4C)alkyl and 1H-tetrazol-5-yl-C 1-4  alkyl; and p is 0, 1, 2 or 3; or a salt or ester thereof, provided that R 1  is not methoxymethyl, modulate metabotropic glutamate receptor function and are useful in treating disorders of the central nervous system.

This application is a U.S. national phase entry, prudent to 35 USC 371,of PCT/EP00/04903, filed May 26, 2000 and published on Dec. 14, 2000,International Publication No. WO 00/75101, which claims the benefit ofEuropean Application No. 99500090.8 filed Jun. 3, 1999.

In the mammalian central nervous system (CNS), the transmission of nerveimpulses is controlled by the interaction between a neurotransmitter,that is released by a sending neuron, and a surface receptor on areceiving neuron, which causes excitation of this receiving neuron.L-Glutamate, which is the most abundant neurotransmitter in the CNS,mediates the major excitatory pathway in mammals, and is referred to asan excitatory amino acid (EAA). The receptors that respond to glutamateare called excitatory amino acid receptors (EAA receptors). See Watkins& Evans, Ann. Rev. Pharmacol. Toxicol., 21, 165 (1981); Monaghan,Bridges, and Comas, Ann. Rev. Pharmacol. Toxicol., 29, 365 (1989);Watkins, Krogsgaard-Larsen, and Honore, Trans. Pharm. Sci., 11, 25(1990). The excitatory amino acids are of great physiologicalimportance, playing a role in a variety of physiological processes, suchas long-term potentiation (learning and memory), the development ofsynaptic plasticity, motor control, respiration, cardiovascularregulation, and sensory perception.

Excitatory amino acid receptors are classified into two general types.Receptors that are directly coupled to the opening of cation channels inthe cell membrane of the neurons are termed “ionotropic”. This type ofreceptor has been subdivided into at least three subtypes, which aredefined by the depolarizing actions of the selective agonistsN-methyl-D-aspartate (NMDA),alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), andkainic acid (KA). The second general type of receptor is the G-proteinor second messenger-linked “metabotropic” excitatory amino acidreceptor. This second type is coupled to multiple second messengersystems that lead to enhanced phosphoinositide hydrolysis, activation ofphospholipase D or C, increases or decreases in c-AMP formation, andchanges in ion channel function. Schoepp and Conn, Trends in Pharmacol.Sci., 14, 13 (1993). Both types of receptors appear not only to mediatenormal synaptic transmission along excitatory pathways, but alsoparticipate in the modification of synaptic connections duringdevelopment and throughout life. Schoepp, Bockaert, and Sladeczek,Trends in Pharmacol. Sci., 11, 508 (1990); McDonald and Johnson, BrainResearch Reviews, 15, 41 (1990).

The excessive or inappropriate stimulation of excitatory amino acidreceptors leads to neuronal cell damage or loss by way of a mechanismknown as excitotoxicity. This process has been suggested to mediateneuronal degeneration in a variety of conditions. The medicalconsequences of such neuronal degeneration makes the abatement of thesedegenerative neurological processes an important therapeutic goal.

The metabotropic glutamate receptors are a highly heterogeneous familyof glutamate receptors that are linked to multiple second-messengerpathways. These receptors function to modulate the presynaptic releaseof glutamate, and the postsynaptic sensitivity of the neuronal cell toglutamate excitation. Compounds which modulate the function of thesereceptors, in particular agonists and antagonists of glutamate, areuseful for the treatment of acute and chronic neurodegenerativeconditions, and as antipsychotic, anticonvulsant, analgesic, anxiolytic,antidepressant, and anti-emetic agents.

Pellicciari et al., J. Med. Chem., 1996, 39, 2259-2269 refers tocompounds known as metabotropic glutamate receptor agonists, inparticular (2S,1′S,2′S)-2-(2-carboxycyclopropyl)glycine, also known asL-CCG-I; (2S,1′S,2′R,3′R)-2-(2′-carboxy-3′-(methoxymethyl)cyclopropyl-glycine, alsoknown as cis-MCG-I;(2S,1′S,2′R,3′S)-2-(2′-carboxy-3′-(methoxymethyl)cyclopropylglycine,also known as trans-MCG-I; and(2S,1′R,2′R,3′R)-2-(2′,3′-dicarboxy-cyclopropyl)glycine, also known asDCG-IV. The paper also describes the synthesis of the sixteen possiblestereoisomers of 2-(2′-carboxy-3′-phenylcyclopropyl)glycine and theirevaluation as excitatory amino acid receptor ligands. The compound(2S,1′S,2′S,3′R)-2-(2′-carboxy-3′-phenylcyclopropyl)glycine, also knownas PCCG 4 is reported to be a metabotropic glutamate receptorantagonist.

Japanese patent application publication number JP 06179643 discloses MCGand generically discloses (2S,1′S,2′R)-2-(2-carboxy-3-alkoxymethyl- and3-aralkoxymethyl-cyclopropyl)glycines as glutamate receptor agonists.

International patent application publication number WO 97/19049discloses PCCG 4 and also generically discloses various2-carboxy-3-arylcyclopropylglycines having affinity for metabotropicglutamate receptors.

International patent application publication number WO 98/00391discloses 2-carboxy-3,3-dihalocyclopropylglycines, including(2S,1′S,2′S)-2-(2-carboxy-3,3-difluoro)-cyclopropylglycine asmetabotropic glutamate receptor agonists.

European patent application, publication number EP-A1-0870760 disclosesthat certain 3-substituted 2-carboxycyclopropyl glycine derivatives aremodulators of metabotropic glutamate receptor function. The preferredcompounds are said to be those in which the substituents at the 1 and 2positions are in a trans relationship. The examples illustrate suchcompounds in which the substituents at the 1 and 3 positions are also ina trans relationship. One such compound is(2S,1′S,2′S,3′S)-2′-carboxy-3′-methylcyclopropylglycine.

Surprisingly, novel 3-substituted 2-carboxycyclopropyl glycinederivatives have now been found which are potent agonists of glutamateat metabotropic glutamate receptors.

Accordingly, the present invention provides a compound of the formula:

in which:

R¹ is halo-C₁₋₁₀ alkyl; halo-C₂₋₁₀ alkenyl; or (CH₂)_(n)Y in which n is1 or 2 and Y is OH, CN, N₃, SH, S(O)_(p)R⁴, S(O)₃H, NH₂, NHR⁵, NR⁶R⁷,NHCOR⁸, NO₂, CO₂H, CONHR⁹, 1H-tetrazol-5-yl, 5-phenyltetrazol-2-yl, orPO₃H₂; R³, R⁵, R⁶, R⁷, R⁸ and R⁹ are each selected independently fromC₁₋₄ alkyl, aryl and aryl-C₁₋₄ alkyl; R⁴ is selected from C₁₋₄ alkyl,aryl, aryl-C₁₋₄ alkyl, 1H-tetrazol-5-yl, carboxy-C₁₋₄ alkyl and1H-tetrazol-5-yl-C₁₋₄ alkyl; and p is 0, 1, 2 or 3;

or a salt or ester thereof.

Compounds of the invention have been found to be agonists of glutamateat metabotropic glutamate receptors and are therefore useful in thetreatment of diseases of the central nervous system such as neurologicaldiseases, for example neurodegenerative diseases, and as antipsychotic,anxiolytic, drug-withdrawal, antidepressant, anticonvulsant, analgesicand anti-emetic agents.

It will be appreciated that the compounds of formula (I) contain atleast four asymmetric carbon atoms, three being in the cyclopropane ringand one being at the α-carbon of the amino acid group. Accordingly, thecompounds of the invention may exist in and be isolated inenantiomerically pure form, in racemic form, or in a diastereoisomericmixture.

Preferred compounds of the invention are those of the formula

The amino acid moiety preferably has the natural amino configuration.Accordingly, preferred compounds according to the invention are those ofthe formula:

As used herein, the term halogen atom, as such or as halo, for exampleas in haloalkyl, includes a fluorine or chlorine atom; a C₁₋₁₀ alkylgroup includes a C₁₋₄ alkyl group and can be straight or branched chain,such as, for example, methyl, ethyl, propyl, isopropyl, butyl andisobutyl, and is preferably methyl or ethyl. A C₂₋₁₀ alkenyl groupincludes, for example, vinyl, prop-2-enyl, but-3-enyl, pent-4-enyl andisopropenyl, and an alkenyl group can contain more than one double bondand, in addition, one or more triple bonds. A preferred alkenyl group isof the formula R′—CH═CH—(CH₂)_(r)— where R′ is hydrogen or C₁₋₄ alkyland r is 0, 1 or 2. An aryl group, as such or in an aryl-C₁₋₄ alkyl maybe, for example, a phenyl group or a substituted phenyl group, forexample with one or two substituents selected independently fromhalogen, C₁₋₄ alkyl and C₁₋₄ alkoxy. An example of an aryl group isphenyl or 3-chlorophenyl. An example of an aryl-C₁₋₄ alkyl group isbenzyl.

A particular sub-group of compounds of formula I is that in which R⁴ isselected from C₁₋₄ alkyl, aryl, aryl-C₁₋₄ alkyl and1H-tetrazol-5-yl-C₁₋₄ alkyl.

Examples of particular values for R¹ are: for a halo-C₁₋₁₀ alkyl group:fluoromethyl; trifluoromethyl; 2-fluoroethyl; trifluorethyl, such as2,2,2-trifluoroethyl; chloromethyl; 2-chloroethyl; trichloromethyl; andtrichloroethyl, such as 2,2,2-trichloroethyl; for a halo-C₂₋₁₀ alkenylgroup: 2-fluorovinyl and 2,2-difluorovinyl; for a (CH₂)_(n)Y group:hydroxymethyl, 2-hydroxyethyl, 2-benzyloxyethyl, cyanomethyl,2-cyanoethyl, azidomethyl, 2-azidoethyl, 2-methoxyethyl, mercaptomethyl;2-mercaptoethyl, methanethiomethyl, 2-methanethioethyl,1H-tetrazol-5-ylthiomethyl, carboxymethylthiomethyl, phenylthiomethyl,methanesulfinylmethyl, 2-methanesulfinylethyl, methanesulfonylmethyl,phenylsulfinylmethyl, phenylsulfonylmethyl, 2-methanesulfonylethyl,2-phenylthioethyl, 2-benzylthioethyl, aminomethyl, acetylaminomethyl,benzoylaminomethyl, 3-chlorobenzoylaminomethyl, benzylamidomethyl,methylaminomethyl, nitromethyl, 2-nitroethyl, 1H-tetrazol-5-ylmethyl,2-(1H-tetrazol-5-yl)ethyl, 5-phenyltetrazol-2-ylmethyl, carboxymethyl,2-carboxyethyl, aminocarbonylmethyl, phosphonomethyl, acetamidomethyl,benzamidomethyl and 2-benzamidoethyl.

Examples of particular values for R³, R⁵, R⁶, R⁷, R⁸ and R⁹ are:

for a C₁₋₄ alkyl group: methyl or ethyl;

for an aryl group: phenyl or 3-chlorophenyl; and for an aryl-C₁₋₄ alkylgroup: benzyl.

Examples of particular values for R⁴ are:

for a C₁₋₄ alkyl group: methyl;

for an aryl group: phenyl;

for an aryl-C₁₋₄ alkyl group: benzyl;

for a carboxy-C₁₋₄ alkyl group: carboxymethyl; and

for a 1H-tetrazol-5-yl-C₁₋₄ alkyl group: 1H-tetrazol-5-ylmethyl.

Preferably R¹ is selected from fluoromethyl, trifluoromethyl,2-fluoroethyl, 2,2,2-trifluoroethyl, chloromethyl, 2-chloroethyl,trichloromethyl, 2,2,2-trichloroethyl, 2-fluorovinyl, 2,2-difluorovinyl,hydroxymethyl, 2-hydroxyethyl, 2-benzyloxyethyl, cyanomethyl,2-cyanoethyl, azidomethyl, 2-azidoethyl, mercaptomethyl,2-mercaptoethyl, methanethiomethyl, 2-methanethioethyl,1H-tetrazol-5-ylthiomethyl, carboxymethylthiomethyl, phenylthiomethyl,methanesulfinylmethyl, 2-methanesulfinylethyl, methanesulfonylmethyl,phenylsulfinylmethyl, phenylsulfonylmethyl, 2-methanesulfonylethyl,2-phenylthioethyl, 2-benzylthioethyl, aminomethyl, acetylaminomethyl,benzoylaminomethyl, 3-chlorobenzoylaminomethyl, benzylamidomethyl,methylaminomethyl, nitromethyl, 2-nitroethyl, 1H-tetrazol-5-ylmethyl,2-(1H-tetrazol-5-yl)ethyl, 5-phenyltetrazol-2-ylmethyl, carboxymethyl,2-carboxyethyl, aminocarbonylmethyl, phosphonomethyl, acetamidomethyl,benzamidomethyl, and 2-benzamidoethyl.

A particular sub-group of compounds of formula I is that in which R¹ isselected from fluoromethyl, 2-fluoroethyl, trifluoromethyl,trichloromethyl, trichloroethyl, 2-trichloroethyl, 2-fluorovinyl,2,2-difluorovinyl, hydroxymethyl, cyanomethyl, 2-cyanoethyl,azidomethyl, 2-azidoethyl, 2-benzyloxyethyl, mercaptomethyl,methanethiomethyl, 2-methanethioethyl, 1H-tetrazol-5-ylthiomethyl,methanesulfinylmethyl, 2-methanesulfinylethyl, methanesulfonylmethyl,2-methanesulfonylethyl, aminomethyl, acetylaminomethyl, nitromethyl,1H-tetrazol-5-ylmethyl, aminocarbonylmethyl, phosphonomethyl,acetamidomethyl and benzamidomethyl. Especially preferred are compoundsin which R¹ is hydroxymethyl.

Particularly preferred compounds are:

(2SR,1′SR,2′RS,3′RS)-2-(3′-hydroxymethyl-2′-carboxycyclopropyl)glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-hydroxyethyl)-2′-carboxy)cyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-mercaptomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-carboxymethylthiomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-(1H-tetrazol-5-ylthiomethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-mercaptoethyl)-2′-carboxy)cyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-methylthiomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-phenylthiomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-phenylthioethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-benzylthioethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-methylsulfonylmethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-phenylsulfonylmethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-azidomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-fluoroethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-chloroethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-acetylaminomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-benzoylaminomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-aminomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-benzylcarbonylaminomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-(m-chlorobenzoyl)aminomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-methylaminomethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′RS,2′RS,3′RS)-2-[3′-trifluoromethyl-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-(1H-tetrazol-5-yl)ethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-azidoethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-nitroethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-benzyloxyethyl)-2′-carboxycyclopropyl]glycine;

(2SR,1′SR,2′SR,3′RS)-2-[3′-(5-phenyltetrazol-2-yl)methyl-2′-carboxycyclopropyl]glycine,

and pharmaceutically acceptable salts and esters thereof.

A compound of especial interest is:(2S,1′S,2′R,3′R)-2-(3′-hydroxymethyl-2′-carboxycyclopropyl)glycine, aswell as the pharmaceutically acceptable salts thereof.

This compound has been found to be highly potent as an agonist ofglutamate at Group II metabotropic glutamate receptors (mGluR2 andmGluR3). It is believed to be the most highly potent2′-carboxycyclopropyl)glycine (CCG) compound made to date.

The present invention includes salts of the formula (I) compounds. Thesesalts can exist in conjunction with the acidic or basic portion of themolecule and can exist as acid addition, primary, secondary, tertiary,or quaternary ammnonium, alkali metal, or alkaline earth metal salts.Generally, the acid addition salts are prepared by the reaction of anacid with a compound of formula (I). The alkali metal and alkaline earthmetal salts are generally prepared by the reaction of the hydroxide formof the desired metal salt with a compound of formula (I).

The salts of the compounds of formula I may bepharmaceutically-acceptable salts. However, other salts are included inthe invention. They may serve as intermediates in the purification ofcompounds or in the preparation of other, for examplepharmaceutically-acceptable, acid addition salts, or are useful foridentification, characterisation or purification.

Acid addition salts are preferably the pharmaceutically acceptable,non-toxic addition salts with suitable acids, such as those withinorganic acids, for example hydrochloric, hydrobromic, nitric,sulphuric or phosphoric acids, or with organic acids, such as organiccarboxylic acids, for example, glycollic, maleic, hydroxymaleic,fumaric, malic, tartaric, citric, salicylic, o-acetoxybenzoic, ororganic sulphonic, 2-hydroxyethane sulphonic, toluene-p-sulphonic, ornaphthalene-2-sulphonic acid.

The present invention includes esters of the formula (I) compounds, suchesters being for example aliphatic esters such as alkyl esters.

The esters of the compounds of formula I may be pharmaceuticallyacceptable metabolically labile esters of compounds of formula I. Theseare ester derivatives of compounds of formula I that are hydrolyzed invivo to afford said compound of formula I and a pharmaceuticallyacceptable alcohol. Examples of metabolically labile esters includeesters formed with (1-6C) alkanols in which the alkanol moiety may beoptionally substituted by a (1-8C) alkoxy group, for example methanol,ethanol, propanol and methoxyethanol. The most preferred esters arealkyl esters derived from (1-4C) alkanols, especially methyl and ethylesters.

The invention also comprises a process for preparing a compoundaccording to formula (I), or a salt or ester thereof, which comprises:

(a) deprotecting a compound of formula

in which R¹⁰ and R¹¹ each independently represents hydrogen or acarboxyl protecting group, and R¹² represents hydrogen or an amineprotecting group;

(b) hydrolysing a compound of formula

in which R¹³ represents a hydrogen atom or a carboxyl protecting group,and R¹⁴ and R¹⁵ each independently represents a hydrogen atom, a C₁₋₄alkyl group, or a phenyl C₁₋₄ alkyl group in which the phenyl group isunsubstituted or substituted by halo, C₁₋₄ alkyl, C₁₋₄ alkoxy or C₃₋₄alkenyl; or

(c) hydrolysing a compound of formula

in which R¹⁶ represents a hydrogen atom or a carboxy protecting group,and R¹⁷ represents a hydrogen atom or an amine protecting group;

followed when necessary by recovering a diastereomer or isomer of thecompound, or

forming a salt or ester thereof.

The protection of carboxylic acid groups is described in McOmie,Protecting Groups in Organic Chemistry, Plenum Press, NY, 1973, andGreene and Wuts, Protecting Groups in Organic Synthesis, 2nd. Ed., JohnWiley & Sons, NY, 1991. Examples of carboxy protecting groups includeC₁-C₆ alkyl groups such as methyl, ethyl, t-butyl and t-amyl;aryl(C₁-C₄)alkyl groups such as benzyl, 4-nitrobenzyl, 4-methoxybenzyl,3,4-dimethoxybenzyl, 2,4-dimethoxybenzyl, 2,4,6-trimethoxybenzyl,2,4,6-trimethylbenzyl, benzhydryl and trityl; silyl groups such astrimethylsilyl and t-butyldimethylsilyl; and allyl groups such as allyland 1-(trimethylsilylmethyl)prop-1-en-3-yl.

Examples of amine protecting groups include acyl groups, such as groupsof formula R¹⁸CO in which R¹⁸ represents C₁₋₆ alkyl, C₃₋₁₀ cycloalkyl,phenyl C₁₋₆ alkyl, phenyl, C₁₋₆ alkoxy, phenyl C₁₋₆ alkoxy, or a C₃₋₁₀cycloalkoxy, wherein a phenyl group may be optionally substituted, forexample by one or two of halogen, C₁-C₄ alkyl and C₁-C₄ alkoxy.Preferred amino protecting groups include t-butoxycarbonyl (Boc) andbenzyl.

Examples of particular values for R¹⁰, R¹¹, R¹³ and R¹⁶ are hydrogen,methyl, ethyl, n-propyl, n-butyl, t-butyl, benzyl, 4-methoxybenzyl,phenylethyl and phenylpropyl.

Examples of particular values for R¹² and R¹⁷ include acetyl andtert-butoxycarbonyl.

Examples of particular values for R¹⁴ and R¹⁵ are hydrogen and benzyl.

The compounds of formula (II) may be deprotected by conventionalmethods. Thus, an alkyl carboxyl protecting group may be removed byhydrolysis. The hydrolysis may conveniently be performed by heating thecompound of formula (II) in the presence of either a base, for examplean alkali metal hydroxide such as lithium, sodium or potassiumhydroxide, or an alkaline metal hydroxide, such as barium hydroxide oran acid such as hydrochloric acid. The hydrolysis is convenientlyperformed at a temperature in the range of from 20° C. to 300° C. Anaralkyl carboxyl protecting group may conveniently be removed byhydrogenation. The hydrogenation may be effected by reacting thecompound of formula (II) with hydrogen in the presence of a Group VIIImetal catalyst, for example a palladium catalyst such as palladium oncharcoal. Suitable solvents for the reaction include alcohols such asethanol. The reaction is conveniently performed at a temperature in therange of from 0° C. to 100° C.

An acyl, amine protecting group is also conveniently removed byhydrolysis, for example as described for the removal of an alkylcarboxyl protecting group. Thus, a tert-butoxycarbonyl, amine protectinggroup may conveniently be removed in the presence of an acid, forexample hydrochloric acid or trifluoroacetic acid. The hydrolysis isperformed in the presence of a solvent such as water, ethyl acetate ordichloromethane and at a temperature in the range of from 20° C. to 100°C.

The compounds of formula III are conveniently hydrolyzed in the presenceof a base, for example an alkali metal hydroxide such as lithium, sodiumor potassium hydroxide, or an alkaline earth metal hydroxide such asbarium hydroxide. Suitable reaction media include water. The temperatureis conveniently in the range of from 50° C. to 150° C.

The compounds of formula IV are conveniently hydrolyzed in the presenceof an acid, such as hydrochloric acid or sulfuric acid, or a base, suchas an alkali metal hydroxide, for example sodium hydroxide. Thehydrolysis is conveniently performed in an aqueous solvent such aswater, or in an alkanol such as methanol or ethanol, and at atemperature in the range of from 20° C. to 200° C.

Compounds of formula I in the form of diastereomeric mixtures or isomersmay be obtained in a conventional manner, for example by chiralsynthesis using chiral starting materials, or by using conventionalseparation techniques, for example by forming a crystalline salt with achiral acid or base, or by chiral hplc.

Compounds of formula (II) in which R¹¹ represents hydrogen may beprepared by a procedure analogous to that described in Ohfune Y., etal., J. Med. Chem., 1996, 39, 407-423. Thus they may be prepared byreacting a compound of formula

with an oxidising agent. Convenient oxidising agents include JonesReagent.

Compounds of formula (V) may be prepared by reacting a compound offormula

with a sulfonic acid, such as camphorsulfonic acid (CSA) and an alkanol,such as methanol.

Compounds of formula (VI) may be prepared by reacting a compound offormula

with a strong base, such as potassium bis(trimethylsilyl)amide.

Compounds of formula (VII) may be prepared by reacting a compound offormula

with acetone dimethyl ketal in the presence of a sulfonic acid, such ascamphorsulfonic acid.

Compounds of formula VIII may be prepared by selectively deprotecting acompound of formula

in which R¹⁹ represents a hydroxyl protecting group, such as atert-butyldimethylsilyl (TBS) group. A convenient reagent for removing aTBS group is camphorsulfonic acid in methanol.

The compounds of formula (IX) may be prepared by reacting a compound offormula

with a base, such as lithium hydroxide, for example in tetrahydrofuran,followed by introduction of the protecting group R¹⁰, for example bytreatment with diazomethane (to afford a compound in which R¹⁰ ismethyl).

Compounds of formula (X) may be prepared by treating a compound offormula

with an ion exchange resin, such as DOWEX 50Wx8, followed byintroduction of the protecting groups R¹² and R¹⁹, for example bystepwise reaction with tributylsilyl chloride in the presence ofimidazole, followed by Boc₂O in the presence of triethylamine and4-dimethylaminopyridine.

Compounds of formula (XI) may be prepared by reacting a compound offormula

with palladium (II) acetate.

Compounds of formula (XII) may be prepared by diazotizing a compound offormula

for example by reaction with sodium nitrite.

Compounds of formula (XIII) may be prepared by selectively deprotectinga compound of formula

in which R²⁰ represents an amine protecting group, such ast-butoxycarbonyl. For example a t-butoxycarbonyl (Boc) group mayconveniently be removed by treatment with trimethylsilyltrifluoromethanesulfonate (TMSOTf) and 2,6-lutidine.

The compounds of formula (XIV) may be prepared by reacting a compound offormula

with an N-protected glycinate, such as N-hydroxysuccinimideN-(tert-butoxycarbonyl)glycinate, followed by reaction with acetonedimethylketal in the presence of a sulfonic acid such asp-toluenesulfonic acid.

The compounds of formula (XV) may be prepared by reacting a compound offormula

in which R²¹ represents an amine protecting group, such ast-butoxycarbonyl, with a triphenylphosphine halide of formula Ph₃P⁺CH₂R¹A⁻, in which A⁻ represents a halide ion such as bromide, in the presenceof a strong base, such as potassium bis(trimethylsilyl)amide, followedby removal of the amine protecting group, and hydrolysis of theacetonide, for example by reaction with methanolic HCl.

Compounds of formula (II) in which R¹ represents (CH₂)_(n)Y in which nis 1 or 2 may alternatively be prepared by reacting a compound offormula

in which n is 1 or 2 and Z¹ represents a leaving atom or group, such asa halogen atom, for example a chlorine atom, an organosulfonyloxy group,for example a p-toluenesulfonyloxy group or a diphenylphosphoryloxygroup, with a salt of formula MY in which M represents an alkali metalsuch as sodium or potassium.

The compounds of formula (XVII) in which Z¹ represents a halogen atom oran organosulfonyloxy group may be prepared by reacting a compound offormula

with a halogenating or sulphonating reagent such as p-toluenesulfonylchloride.

Compounds of formula (XVII) in which Z¹ represents adiphenylphosphoryloxy group may be prepared by reacting a compound offormula (XVIII) with diphenyl-phosphoryl azide in the presence ofdiazabicyclo[5.4.0]-undec-7-ene. Convenient solvents include aromatichydrocarbons, such as toluene. The reaction is conveniently effected ata temperature of from 0 to 100° C.

Compounds of formula (XVIII) may be converted directly into compounds offormula (II) in which R¹ represents (CH₂)_(n)Y and Y is N₃ by reactionwith diethylazodicarboxylate and triphenylphosphine followed bydiphenylphosphoryl azide. The reaction is conveniently conducted in ananhydrous ether solvent, such as tetrahydrofuran and under an inertatmosphere, such as nitrogen. The temperature is conveniently in therange of from −50 to 40° C.

Compounds of formula (XVII) in which Z¹ represents adiphenylphosphoryloxy group, may be also converted into compounds offormula (II) in which R¹ represents (CH₂)_(n)Y and Y is N₃ by reactionwith sodium azide. The reaction is conveniently conducted in ananhydrous solvent, such as N,N-dimethylformamide and under an inertatmosphere, such as nitrogen. The temperature is conveniently in therange of from 0 to 100° C.

Compounds of formula (XVIII) may be converted directly into compounds offormula (II) in which R¹ represents (CH₂)_(n)Y and Y is F by reactionwith a fluorinating agent, such as (diethylamino)sulfur trifluoride.Convenient solvents for the reaction include halogenated hydrocarbons,such as dichloromethane. The reaction is conveniently performed at atemperature of from 0 to 100 ° C.

Compounds of formula (XVIII) may be converted directly into compounds offormula (II) in which R¹ represents (CH₂)_(n)Y and Y is Cl by reactionwith a chlorinating agent, such as carbon tetrachloride andtriphenylphosphine. Convenient solvents for the reaction include amides,such as dimethylformamide. The reaction is conveniently performed at atemperature of from 0 to 100° C.

Compounds of formula (XVIII) may be converted directly into compounds offormula (II) in which R¹ represents (CH₂)_(n)Y and Y is S(O)_(p)R⁴ and pis 0 by reaction with a compound of formula R⁴SH,diethylazodicarboxylate and triphenylphosphine. The reaction isconveniently conducted in an anhydrous ether solvent, such astetrahydrofuran and under an inert atmosphere, such as argon. Thetemperature is conveniently in the range of from −10 to 100° C. If,instead of a compound of formula R⁴SH, thioacetic acid is used, theresultant compound is a compound of formula (II) in which Y is SCOCH₃and this, on deprotection according to process step (a) above, affords acompound of formula (I) in which Y is SH. Alternatively the compound offormula (XVIII) may be reacted with a disulfide of formula (R⁴S)₂ andtributylphosphine. The reaction is conveniently conducted in ananhydrous ether solvent, such as tetrahydrofuran and under an inertatmosphere, such as argon. The temperature is conveniently in the rangeof from −10 to 100° C. Compounds of formula (II) in which R¹ represents(CH₂)_(n)Y, Y is S(O)_(p)R⁴ and p is 0 may be converted into thecorresponding compounds in which p is 1 or 2 by reaction with a peracid,such as m-chloroperbenzoic acid. Convenient solvents include halogenatedhydrocarbons, such as dichloromethane. The reaction is convenientlyperformed at temperature in the range of from −10 to 50° C.

Compounds of formula (XVIII) may be converted directly into compounds offormula (II) in which R¹ represents (CH₂)_(n)Y and Y is5-phenyltetrazol-2-yl by reaction with 5-phenyl-1H-tetrazole, diethylazodicarboxylate and triphenylphosphine. The reaction is convenientlyconducted in an anhydrous ether solvent, such as tetrahydrofuran andunder an inert atmosphere, such as nitrogen. The temperature isconveniently in the range of from 0 to 100° C.

The compounds of formula XVIII may be prepared either by hydrolysing acompound of formula XIX

for example using HCl in aqueous ethanol, followed by protecting theamino group, for example by reaction with Boc₂O in tetrahydrofuran ordioxane in the presence of NaHCO₃, or by hydrolysing a compound offormula XX

in the presence of a base, for example sodium hydroxide, in an aqueoussolution at an elevated temperature, for example about 100° C., followedby protecting the carboxylic acid groups, for example using HCl inanhydrous ethanol, and protecting the amino group, for example byreaction with Boc₂O in tetrahydrofuran or dioxane in the presence ofNaHCO₃.

The compounds of formula XIX may be prepared by reacting a compound offormula XXI

with ammonium chloride and potassium cyanide in the presence ofaluminium oxide. A convenient solvent is acetonitrile.

The compounds of formula XX may be prepared by hydrolysing a compound offormula XXI with an alkali metal hydroxide, for example using sodiumhydroxide in aqueous ethanol, followed by treatment with an alkali metalcyanide, such as lithium, sodium or potassium cyanide, and ammoniumcarbonate in an aqueous alcohol, such as aqueous ethanol. Convenientlythe reaction is performed at a temperature of from 35° C. to 150° C.

Compounds of formula XXI in which n is 1 may be prepared by oxidising acompound of formula XXII

for example by employing a Swern oxidation.

Compounds of formula XXII may be prepared by reacting a compound offormula

in which R²² represents a hydrogen atom, a C₁₋₄ alkyl group or a phenylgroup, with HCl or camphorsulphonic acid in an alkanol such as ethanol.

Compounds of formula XXIII may be prepared by reacting a compound offormula

with N₂CHCO₂R¹⁰ in the presence of Rh₂(OAc)₄. A convenient solvent ispentane.

Compounds of formula XXI in which n is 2 may be prepared by reducing acompound of formula

for example using diisobutylaluminium hydride.

Compounds of formula (XXIg) may be prepared by reacting a compound offormula

with a peracid, such as m-chloroperbenzoic acid.

After they have been prepared, compounds of formula (II) may beconverted into other compounds of formula (II) prior to deprotectionaccording to process step (a) hereinabove. For example, a compound offormula (II) in which R¹ is (CH₂)_(n)Y and Y is N₃ may be reduced in thepresence of an alkylating, such as a C₁₋₄ alkyl or aryl-C₁₋₄ alkylhalide to afford a compound of formula (II) in which R¹ is (CH₂)_(n)Y, Yis NHR⁵, and R⁵ is C₁₋₄ alkyl or aryl-C₁₋₄ alkyl. The reduction isconveniently performed by catalytic hydrogenation in the presence of aGroup VIII metal catalyst, such as palladium on carbon or platinumoxide. Similarly, a compound of formula (II) in which R¹ is (CH₂)_(n)Yand Y is NHCOR⁸ may be prepared by reducing a compound of formula (II)in which R¹ is (CH₂)_(n)Y and Y is N₃ in the presence of an anhydride offormula (R⁸CO)₂CO. The reduction is conveniently performed by catalytichydrogenation in the presence of a Group VIII metal catalyst, such aspalladium on carbon or platinum oxide. Alternatively, the reduction andalkylation or acylation steps may be performed sequentially. It will beappreciated by those skilled in the art that deprotection of a compoundof formula (II) in which R¹ is (CH₂)_(n)Y and Y is NHCOR⁸ according toprocess step (a) may, depending upon the reaction conditions selected,afford a compound of formula (I) in which Y is NHCOR⁸ or NH₂.

A compound of formula (II) in which R¹ is (CH₂)_(n)Y and Y is CN may beconverted directly into a compound of formula (I) in which R¹ is(CH₂)_(n)Y and Y is COOH by acid catalysed hydrolysis, for example usinghydrochloric acid.

A compound of formula (II) in which R¹ is (CH₂)_(n)Y and Y is CN may beconverted into a compound of formula (II) in which R¹ is (CH₂)_(n)Y andY is 1H-tetrazol-5-yl by reaction with a trialkyltin azide such astributyltin azide.

A compound of formula (II) in which R¹ is (CH₂)_(n)Y and Y is NH₂ may beconverted into a compound of formula (II) in which R¹ is (CH₂)_(n)Y andY is NO₂ by reaction with a peracid, such as m-chloroperbenzoic acid.

The compounds of formula (III) may be prepared by reacting a compound offormula

with an alkali metal cyanide, such as lithium, sodium or potassiumcyanide, and ammonium carbonate in an aqueous alcohol, such as aqueousethanol. Conveniently the reaction is performed at a temperature of from35° C. to 150° C. If desired, the compounds of formula (III) may then bealkylated, for example using a compound of formula R¹⁴Cl or R¹⁵Cl. Thealkylated compounds are readily separated into their diastereomers.

Compounds of formula (IV) may be prepared by reacting a compound offormula (XXV), in which R¹⁶ is as defined for R¹³, with an alkali metalcyanide, such as lithium, sodium or potassium cyanide, and an ammoniumhalide, such as ammonium chloride. It has been found advantageous toperform the reaction in the presence of ultrasound. Thus, the ammoniumhalide and alkali metal cyanide are advantageously mixed withchromatography grade alumina in the presence of a suitable diluent, suchas acetonitrile. The mixture is then irradiated with ultrasound,whereafter the compound of formula XXV is added, and the mixture isagain irradiated.

The resultant mixture of diastereoisomeric aminonitriles may then bereacted with an acylating agent, such as acetyl chloride in the presenceof a suitable base, for example an amine such as diisopropylamine, andin the presence of a suitable solvent such as dichloromethane, to afforda mixture of diastereomeric acylaminonitriles. The desired stereoisomermay conveniently be separated from this mixture, for example bychromatography.

The compounds of formula (XXV) may be prepared by oxidising a compoundof formula

for example by a Swern oxidation or by reaction with tetrapropylammoniumperruthenate and N-methylmorpholine-N-oxide in the presence of amolecular sieve (4 Å).

A compound of formula (XXV) having the configuration

may be converted into a mixture of compounds of formula (XXV) containinga compound of the configuration

by treatment with methanolic sodium hydroxide, if necessary followed byreintroduction of the protecting group R¹⁶, for example by reaction withdiazomethane to afford a compound in which R¹⁶ is methyl.

The compounds of formula (XXVI) may be prepared by selectivelydeprotecting a compound of formula

in which R²³ represent a hydroxyl protecting group, for example a benzylgroup. The deprotection may be performed in a conventional manner. Forexample, a benzyl group may be removed by catalytic hydrogenation usingpalladium on charcoal as catalyst.

Compounds of formula (XXVI) having the configuration

may be prepared by reacting a compound of formula

with an alkali metal hydroxide, such as lithium hydroxide, to afford acompound in which R¹⁶ represents hydrogen, followed by followed byintroducing a protecting group R¹⁶, for example by reaction withdiazomethane to produce a compound in which R is methyl.

The compounds of formula (XXVIII) may be prepared by reacting a compoundof formula

with Cu(TBS)₂.(copper (II) N-(tert-butyl)salicylaldimine).

The compounds of formula (XXIX) may be prepared by reacting a compoundof formula

with a sulfonyl azide such as p-acetamidobenzenesulfonyl azide in thepresence of a base, such as triethylamine, followed by reaction with anaqueous alkali metal hydroxide, such as lithium hydroxide.

The compounds of formula (XXX) may be prepared by reacting a compound offormula

with diketene in the presence of an alkali metal acetate, such as sodiumacetate.

Compounds of formula (XXV) in which R¹ represents fluoromethyl may beprepared by protecting one hydroxy group in a diol compound of formula(XXII), for example with a benzyl group, followed either by reactionwith a fluorinating agent, such as (diethylamino)sulfur trifluoride, orby functionalization of the remaining hydroxyl group with a leaving atomor group such as an iodine atom or p-toluenesulfonyloxy group thenreaction with an alkali metal fluoride), followed by removal of thehydroxy protecting group.

Compounds of formula (II) may also be prepared by reacting a compound offormula

with a Wittig reagent. For example, a compound of formula (XXXII) may bereacted with a haloalkyl triphenylphosphonium bromide to afford acompound of formula (II) in which R¹ represents a haloalkenyl group. Theresultant product may then, if desired, be converted into anothercompound of formula (II), for example by catalytic hydrogenation toconvert a haloalkenyl group to a haloalkyl group.

Compounds of formula (XXXII) may be prepared by Swern oxidation of acompound of formula (II) in which R¹ represents hydroxymethyl.

It will be appreciated that in order to obtain a compound of formula Iwhich is in the configuration of formula Ia, the intermediates must beprepared in the appropriate configurations. The following formulaillustrate the respective configurations for each of the intermediates.

As described hereinabove, the compounds of the invention are useful forthe treatment of disorders of the central nervous system.

According to another aspect therefore, the present invention provides amethod of treating a patient suffering from or susceptible to a disorderof the central nervous system, which comprises administering aneffective amount of a compound of formula I as defined hereinabove, or apharmaceutically acceptable metabolically labile ester thereof, or apharmaceutically acceptable salt thereof.

The particular effective amount or dose of compound administeredaccording to this invention will of course be determined by theparticular circumstances surrounding the case, including the compoundadministered, the route of administration, the particular conditionbeing treated, and similar considerations. The compounds can beadministered by a variety of routes including oral, rectal, transdermal,subcutaneous, intravenous, intramuscular, or intranasal routes.Alternatively, the compound may be administered by continuous infusion.A typical daily dose will contain from about 0.01 mg/kg to about 100mg/kg of the active compound of this invention. Preferably, daily doseswill be about 0.05 mg/kg to about 50 mg/kg, more preferably from about0.1 mg/kg to about 25 mg/kg.

A variety of physiological functions have been shown to be subject toinfluence by excessive or inappropriate stimulation of excitatory aminoacid transmission. The formula I compounds of the present invention arebelieved to have the ability to treat a variety of neurologicaldisorders in patients associated with this condition, including acuteneurological disorders such as cerebral deficits subsequent to cardiacbypass surgery and grafting, stroke, cerebral ischemia, spinal cordtrauma, head trauma, perinatal hypoxia, cardiac arrest, and hypoglycemicneuronal damage. The formula I compounds are believed to have theability to treat a variety of chronic neurological disorders, such asAlzheimer's disease, Huntington's Chorea, amyotrophic lateral sclerosis,AIDS-induced dementia, ocular damage and retinopathy, cognitivedisorders, and idiopathic and drug-induced Parkinson's. The presentinvention also provides methods for treating these disorders whichcomprises administering to a patient in need thereof an effective amountof a compound of formula I or a pharmaceutically acceptablemetabolically labile ester thereof, or a pharmaceutically acceptablesalt thereof.

The formula I compounds of the present invention are also believed tohave the ability to treat a variety of other neurological disorders inpatients that are associated with glutamate dysfunction, includingmuscular spasms, convulsions, migraine headaches, urinary incontinence,psychosis, (such as schizophrenia), drug tolerance and withdrawal (suchas nicotine, opiates and benzodiazepines), anxiety and relateddisorders, emesis, brain edema, chronic pain, and tardive dyskinesia.The formula I compounds are also useful as antidepressant and analgesicagents. Therefore, the present invention also provides methods fortreating these disorders which comprise administering to a patient inneed thereof an effective amount of the compound of formula I, or apharmaceutically acceptable metabolically labile ester thereof, or apharmaceutically acceptable salt thereof.

The term “treating” for purposes of the present invention, includesprophylaxis, amelioration or elimination of a named condition once thecondition has been established.

The term “patient” for purposes of the present invention is defined asany warm blooded animal such as, but not limited to, a mouse, guineapig, dog, horse, or human. Preferably, the patient is human.

According to another aspect, the present invention provides a compoundof formula I as defined hereinabove, or a pharmaceutically acceptablemetabolically labile ester thereof, or a pharmaceutically acceptablesalt thereof, for use as a pharmaceutical.

According to yet another aspect, the present invention provides the useof a compound of formula I as defined hereinabove, or a pharmaceuticallyacceptable metabolically labile ester thereof, or a pharmaceuticallyacceptable salt thereof, for the manufacture of a medicament fortreating a disorder of the central nervous system.

The ability of compounds to modulate metabotropic glutamate receptorfunction may be demonstrated by examining their ability to influenceeither cAMP production (mGluR 2, 3, 4, 6, 7 or 8) or phosphoinositidehydrolysis (mGluR 1 or 5) in cells expressing these individual humanmetabotropic glutamate receptor (mGluR) subtypes. (D. D. Schoepp, etal., Neuropharmacol., 1996, 35, 1661-1672 and 1997, 36, 1-11).

In these tests the compound of Example 1 of the present application wasfound to reverse [3H] LY341495 binding with a Ki of 66.1 nM at mGluR2and 7.9 nM at mGluR3 (average result from several tests). The compoundof Example 22, which is an anantiomer of the compound of Example 1, wasfound to give a Ki of 30.5 nM for mGluR2 and 5.1 nM for mGluR3.(LY341495 is described in Ornstein et al., J. Med. Chem., 1998, 41,346-357 and J. Med. Chem., 1998, 41, 358 to 378).

The ability of compounds to function as agonists of glutamate atmetabotropic glutamate receptors may be determined by measuring theirability to decrease forskolin-stimulated cAMP in cells expressing mGluRreceptors. The compound of Example 1 gave an EC₅₀ in this test of 5.2 nMfor mGluR2 and 11.5 nM for mGluR3.

The ability of compounds of formula I to treat anxiety and relateddisorders may be demonstrated using the well known fear-potentiatedstartle and elevated plus maze models of anxiety, as described in Davis,Psychopharmacology, 62:1; 1979, Lister, Psychopharmacology, 92: 180-185;1987 and U.S. Pat. No. 5,750,566. The compound of Example 1 has beenfound to be highly potent in an animal model of anxiety.

The compounds of the present invention are preferably formulated priorto administration. Therefore, another aspect of the present invention isa pharmaceutical formulation comprising a compound of formula I, apharmaceutically acceptable metabolically labile ester thereof, or apharmaceutically acceptable salt thereof, and apharmaceutically-acceptable carrier, diluent, or excipient. The presentpharmaceutical formulations are prepared by known procedures usingwell-known and readily available ingredients. In making the compositionsof the present invention, the active ingredient will usually be mixedwith a carrier, or diluted by a carrier, or enclosed within a carrier,and may be in the form of a capsule, sachet, paper, or other container.When the carrier serves as a diluent, it may be a solid, semi-solid, orliquid material which acts as a vehicle, excipient, or medium for theactive ingredient. The compositions can be in the form of tablets,pills, powders, lozenges, sachets, cachets, elixirs, suspensions,emulsions, solutions, syrups, aerosols, ointments containing, forexample, up to 10% by weight of active compound, soft and hard gelatincapsules, suppositories, sterile injectable solutions, and sterilepackaged powders.

Some examples of suitable carriers, excipients, and diluents includelactose, dextrose, sucrose, sorbitol, mannitol, starches, gum, acacia,calcium phosphate, alginates, tragacanth, gelatin, calcium silicate,microcrystalline cellulose, polyvinylpyrrolidone, cellulose, watersyrup, methyl cellulose, methyl and propyl hydroxybenzoates, talc,magnesium stearate, and mineral oil. The formulations can additionallyinclude lubricating agents, wetting agents, emulsifying and suspendingagents, preserving agents, sweetening agents, or flavoring agents.Compositions of the invention may be formulated so as to provide quick,sustained, or delayed release of the active ingredient afteradministration to the patient by employing procedures well known in theart.

The compositions are preferably formulated in a unit dosage form, eachdosage containing from about 5 mg to about 500 mg, more preferably about25 mg to about 300 mg of the active ingredient. The term “unit dosageform” refers to a physically discrete unit suitable as unitary dosagesfor human subjects and other mammals, each unit containing apredetermined quantity of active material calculated to produce thedesired therapeutic effect, in association with a suitablepharmaceutical carrier, diluent, or excipient. The following formulationexamples are illustrative only and are not intended to limit the scopeof the invention in any way.

Formulation 1 Hard Gelatin Capsules are Prepared Using the FollowingIngredients

Quantity (mg/capsule) Active Ingredient 250 Starch, dried 200 Magnesiumstearate 10 Total 460 mg

The above ingredients are mixed and filled into hard gelatin capsules in460 mg quantities.

Formulation 2 Tablets Each Containing 60 mg of Active Ingredient areMade as Follows

Active Ingredient 60 mg Starch 45 mg Microcrystalline cellulose 35 mgPolyvinylpyrrolidone 4 mg Sodium carboxymethyl starch 4.5 mg Magnesiumstearate 0.5 mg Talc 1 mg Total 150 mg

The active ingredient, starch, and cellulose are passed through a No. 45mesh U.S. sieve and mixed thoroughly. The solution ofpolyvinylpyrrolidone is mixed with the resultant powders which are thenpassed through a No. 14 mesh U.S. sieve. The granules so produced aredried at 50° C. and passed through a No. 18 mesh U.S. sieve. The sodiumcarboxymethyl starch, magnesium stearate, and talc, previously passedthrough a No. 60 mesh U.S. sieve, are then added to the granules which,after mixing, are compressed on a tablet machine to yield tablets eachweighing 150 mg.

The following Examples illustrate the invention. In the Examples, theterm “Garner's aldehyde” signifies 1,1-dimethylethyl (S) or(R)-4-formyl-2,2-dimethyl-3-oxazolidine carboxylate, Ph₃PEtBr signifies(ethyl)triphenylphosphonium bromide, KHMDS and LiHMDS signify potassiumand lithium bis(trimethylsilyl)amide respectively, Et₂O signifiesdiethylether, AcOEt signifies ethyl acetate, MeOH signifies methanol,Boc signifies t-butoxycarbonyl, Et₃N signifies triethylamine, THFsignifies tetrahydrofuran, TMSOTf signifies trimethylsilyltrifluoromethanesulfonate, Pd(OAc)₂ signifies palladium acetate, DMFsignifies dimethylformamide, DMAP signifies 4-dimethylaminopyridine,Jones Reagent signifies a solution of 1.0 g of Na₂Cr₂O₇.2H₂O and 1.34 gof sulfuric acid in H₂O (total volume 5 ml), DBU signifies1,8-diazabicyclo[5.4.0]undec-7-ene and DME signifies ethylene glycoldimethyl ether.

a) Ethyl 2,3-dihydroxymethylcyclopropane carboxylate

To a solution of cis-4,7-dihydro-1,3-dioxepin (4.57 g, 45.6 mmol) inpentane (25 mL) under nitrogen at room temperature, Rh₂(OAc)₄ (220 mg,0.5 mmol) was added. To the resulting suspension vigorously stirred, asolution of ethyl diazoacetate (10.5 mL, 100 mmol) in pentane (75 mL)was added dropwise at room temperature over a period of 3-4 hours. Afterthe addition was completed, solvent was removed under vacuo and residuewas chromatographed using a gradient of AcOEt/Hexane 1:10 to 1:5 aseluent. 6.75 g of an inseparable mixture of cyclopropanated product andEtO₂CCH═CHCO₂Et was obtained. A solution of this mixture in ethanolsaturated with hydrogen chloride (250 mL) was stirred overnight at roomtemperature. The following day, solvent was removed under vacuo andresidue taken into ethanol (100 mL). This solution was neutralized withNaHCO₃ (solid), filtered and concentrated. The resulting residue waschromatographed using a gradient of AcOEt/Hexane 1:1 to 3:1 as eluent togive 4.3 g (56% yield) of diol. ¹H-NMR (200 MHz, CDCl₃): 1.23 (t, J=7.1Hz, 3H), 1.49 (t, J=3.5, 1H), 1.89-2.00 (m, 2H), 2.72 (br s, 2H),3.31-3.42 (m, 2H),4.05-4.16 (m, 2H) and 4.10 ppm (c, J=7.1 Hz, 2H).

¹³NMR (50 MHz, CDCl₃): 14.0, 23.8, 27.1 (2C), 60.3 (2C), 60.8 and 172.8ppm.

b) (2SR) and (2RS) Ethyl (1RS,5SR,6RS)-2-hydroxy-3-oxabicyclo[3.1.0]-hexane-6-carboxylate

To a solution of oxalyl chloride (0.38 mL, 4.48 mmol) in CH₂Cl₂ (20 mL)at −78° C. under nitrogen atmosphere, dimethylsulfoxide (0.66 mL, 9.33mmol) was added and stirred for 20 minutes. To this mixture, a solutionof the product of step a) (650 mg, 3.73 mL) in CH₂Cl₂ was added andreaction was stirred at the same temperature for 30 minutes. Then,triethylamine (2.6 mL, 18.65 mmol) was added and mixture allowed toreact at room temperature. After 30 minutes, the reaction mixture wasquenched with water, the layers were separated and the aqueous layer wasextracted with CH₂Cl₂ (2×). The combined organic layers were dried(Na₂SO₄), filtered and evaporated to give a residue which waschromatographed using a gradient of AcOEt/Hexane 1:2 to 1:1 as eluent togive 470 mg (73% yield) of lactol. ¹H-NMR (200 MHz, CDCl₃): 1.23 (t,J=7.1 Hz, 3H), 1.43 (t, J=3.3 Hz, 1H), 2.21-2.23 (m, 2H), 2.76 (d, J=3.0Hz, 1H), 3.85 (d, J=8.7 Hz, 1H), 4.06 (d, J=8.7 Hz, 1H), 4.10 (c, J=7.1Hz, 2H) and 5.32 (d, J=3.0 Hz, 1H). ¹³C-NMR (50 MHz, CDCl₃): 14.1, 22.1,25.0, 31.2, 60.8, 67.3, 97.8 and 171.9 ppm.

c) (2SR) and(2RS)-2-(1′SR,2′RS,3′RS)-2′-(ethoxycarbonyl)-3′-hydroxymethylcyclopropyl]glycinonitrile

A suspension of ammonium chloride (2.42 g, 45.3 mmol) and neutralaluminium oxide (1.4 g) in acetonitrile (50 mL) was ultrasonicated forone hour. A solution of the product of step b) (780 mg, 4.53 mmol) inacetonitrile (20 mL) was then added and ultrasonicated for one hour.After potassium cyanide (3.54 g, 54.36 mmol) finely powdered was added,the mixture was allowed to react for 15 hours. Then, additionalaluminium oxide (3.2 g) was added and the reaction mixture wasultrasonicated for 4 days. The mixture was then filtered through celiteand the inorganics washed with acetonitrile to give 710 mg (78% yield)of the four possible aminonitriles as a yellow oil.

d) (Alternative 1) Ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethylcyclopropyl]glycinate

A solution of the product of step c) (380 mg, 1.92 mmol) in ethanolsaturated with hydrogen chloride (20 mL) and H₂O (0.10 mL, 5.75 mmol)was stirred for one hour at 0° C. and for 48 hours at room temperature.The following day, the solvent was removed in vacuo and the residue wasdissolved in ethanol (25 mL). Then, the solution was neutralized withNaHCO₃ (solid), filtered through celite and concentrated to dryness. Theresulting residue was taken into dioxane(20 mL), and a saturated aqueoussolution of NaHCO₃ (5 mL) was added. Then, a solution ofdi-tert-butyldicarbonate (500 mg, 2.3 mmol) in dioxane (5 mL) was addedand mixture stirred overnight. The layers were then separated and theaqueous layer was extracted with ethyl acetate (AcOEt). The combinedorganic layers were dried (Na₂SO₄), filtered and concentrated todryness. The residue was purified by column chromatography usingAcOEt/Hexane 1:2 as eluent to give 400 mg of a 1:2 mixture ofdiastereoisomers (61% overall yield). The minor and desired isomer(lower Rf) was separated by column chromatography using AcOEt/Hexane 1:3as eluent giving rise to ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethylcyclopropyl]glycinateas a mixture of enantiomers.

d) (Alternative 2) Ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethylcyclopropyl]glycinate

A solution of the product of step b) (1.8 g, 10.45 mmol) in EtOH (65 mL)and NaOH(1N) (63 mL, 63.0 mmol) was stirred at 60° C. for 1 hour. Themixture was then cooled to 0° C and the pH was adjusted to ˜6 byaddition of 1N KHSO₄. To the resulting solution, (NH₄)₂CO₃ (10.1 g,104.5 mmol) and NaCN (1.02 g, 20.9 mmol) were added. The mixture wasstirred under reflux overnight (16-17 hours) and then cooled to roomtemperature. The solution was then evaporated to dryness under vacuo togive a residue that was taken into MeOH and filtered off. The inorganicswere washed with MeOH and the combined methanolic filtrates wereconcentrated in vacuo. The resulting residue was dissolved in 1N NaOH(200 mL) and the mixture was stirred under reflux for 48 hours and thencooled to 0° C. The pH was then adjusted to 1-2 by addition of 1N HCl,and the solvent was removed under vacuo.

The resulting residue was dissolved in a 1N HCl/ethanol solution (250mL) and the mixture was stirred overnight at room temperature. Thesolvent was then removed under vacuo and the residue was taken into EtOH(200 mL). After the solvent was removed under vacuo, the residue wasagain taken into EtOH (200 mL) and the solution neutralized with NaHCO₃(solid), the inorganics filtered off and the filtrate concentrated todryness. The residue was taken into dioxane (200 mL) at room temperatureand a saturated aqueous solution of NaHCO₃ (50 mL) was added. Then, asolution of di-tert-butyldicarbonate (2.75 g, 12.54 mmol) in dioxane (50mL) was added dropwise and the mixture was vigorously stirred at roomtemperature overnight. The mixture was then diluted with AcOEt and thelayers were separated. The aqueous layer was extracted with AcOEt (2×)and the combined organic layers were dried (Na₂SO₄), filtered andconcentrated to dryness. The residue was purified by columnchromatography using AcOEt/hexane (1:2) as eluent to give 2.15 g of a2.3:1 mixture of diastereoisomers (60% overall yield). The major anddesired isomer (lower Rf) was separated by column chromatography usingEt₂O/Hexane 1:1 as eluent giving rise to ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethylclopropyl]glycinateas a mixture of enantiomers.

1H-NMR (200 MHz, CDCl₃): 1.25 (t, J=7.1 Hz, 3H), 1.32 (t, J=7.1 Hz, 3H),1.45 (s, 9H), 1.70-1.81 (m, 2H), 1.91-2.11 (m, 1H), 3.17 (dd, J=3.1,10.1 Hz, 1H), 3.54-3.67 (m, 1H), 3.95-4.33 (m, 6H), and 5.20 ( br d,J=7.3 Hz, 1H).

¹³C-NMR (50 MHz, CDCl₃): 14.0, 14.1, 22.5, 28.2 (3C), 28.9, 29.2, 52.3,60.8, 61.0, 62.5, 80.4, 155.3, 171.8 and 172.4 ppm.

e)(2SR,1′SR,2′RS,3′RS)-2-(3′-hydroxymethyl-2′-carboxycyclopropyl)glycine

To a solution of ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethylcyclopropyl]glycinate(145 mg, 0.42 mmol) in THF (3.5 mL) was added 2.5N LiOH (6.7 mL, 16.8mmol). The mixture was vigorously stirred overnight. The organic layerwas separated and discarded and the aqueous layer was washed with Et₂O.After the aqueous solution was adjusted to pH˜1 by addition of 1N HCl at0° C., it was extracted four times with AcOEt, and the combined organiclayers were dried over Na₂SO₄ and evaporated in vacuo. A solution of theresidue in 2N HCl (3.5 mL) was stirred overnight. The solvent was thenremoved in vacuo and the resulting solid was washed with Et₂O. Thehydrochloride was dissolved in MeOH (3 mL) and propylene oxide (10 mL)was added. The mixture was stirred overnight and the resulting insolublesolid was filtered and washed with Et₂O to give the title compound (55mg, 69%).

¹H-NMR (200 MHz, D₂O): 1.77-2.11 (m, 3H), 3.62 (d, J=11.0 Hz, 1H), 3.66(dd, J=8.6, 12.5 Hz, 1H) and 3.90 ppm (dd, J=6.0, 12.5 Hz, 1H).

¹³C-NMR (50 MHz, D₂O): 25.0, 27.7, 29.1, 54.8, 61.0, 173.9 and 177.9ppm.

a) Ethyl (1SR,5RS,6SR)-2-oxo-bicyclo[3.1.0]hexane-6-carboxylate

To a suspension of ethyl (dimethylsulfonium)acetate bromide (13.9 g,60.9 mmol) in chloroform (60 mL), DBU (9.18 mL, 60.9 mmol) was added.The resulting suspension was vigorously stirred at room temperature for30 minutes. Then, cyclopentenone (5.10 mL, 60.9 mmol) was added and themixture stirred overnight at room temperature. The following dayadditional chloroform (60 mL) was added. The organic layer was washedwith 40 mL of 0.5 N HCl, dried over magnesium sulfate, filtered andevaporated in vacuo. The residue was purified by column chromatographyusing ethyl acetate:hexane 1:9 as eluent to give 8.4 g (82% yield) ofethyl (1SR,5RS,6SR)-2-oxo-bicyclo[3.1.0]hexane-6-carboxylate as acolorless oil.

¹H-NMR (300 MHz, CDCl₃): 1.22 (t, J=7.1 Hz, 3H), 1.95-2.24 (m, 6H),2.44-2.49 (m, 1H), 4.10 (q, J=7.1 Hz, 2H).

¹³C-NMR (75 MHz, CDCl₃): 14.0, 22.3, 26.3, 29.1, 31.7, 35.6, 61.1,170.3, 211.8 ppm.

b) Ethyl (1SR,6SR,7SR)-2-oxo-3-oxa-bicyclo[4.1.0]-heptane-7-carboxylate

To a stirred solution of ethyl(1SR,5RS,6SR)-2-oxo-bicyclo[3.1.0]hexane-6-carboxylate (34.8 g, 207.2mmol) in dichloromethane (300 mL), 70% m-chloroperbenzoic acid (51.1 g,207.2 mmol) was added and refluxed overnight. The following day,additional 70% m-chloroperbenzoic acid (51.1 g, 207.2 mmol) was addedand reflux continued for 15 hours. After that time, the mixture wasdiluted with dichloromethane (200 mL), filtered and washed with 10%Na₂SO₃ (2×200 mL) and with a saturated aqueous solution of sodiumbicarbonate (2×200 mL). The organic layer was dried over magnesiumsulfate, filtered and evaporated in vacuo. The residue was purified bycolumn chromatography using ethyl acetate and hexane 1:2 as eluent togive 22.89 g (60% yield) of ethyl(1SR,6SR,7SR)-2-oxo-3-oxa-bicyclo[4.1.0]heptane-7-carboxylate as acolorless oil.

¹H-NMR (300 MHz, CDCl₃): 1.24 (t, J=7.1 Hz, 3H), 1.97-2.04 (m, 1H),2.13-2.28 (m, 3H), 2.38 (dd, J₁=8.3 Hz, J₂=3.3 Hz, 1H), 2.53 (t, J=3.9Hz, 1H), 4.02 (td, J₁=8.8, Hz, J₂=3.3 Hz, 1H), 4.13 (q, J=7.1 Hz, 2H),4.23-4.31 (m, 1H).

¹³C-NMR (75 MHz, CDCl₃): 14.1, 19.4, 21.4, 22.2, 24.2, 61.5, 64.3,167.8, 170.0 ppm.

c) (2RS) and (2SR) Ethyl(1SR,6RS,7SR)-2-hydroxy-3-oxa-bicyclo[4.1.0]heptane-7-carboxylate

To a solution of ethyl(1SR,6SR,7SR)-2-oxo-3-oxa-bicyclo[4.1.0]heptane-7-carboxylate (15.2 g,82.8 mmol) in anhydrous tetrahydrofuran (300 mL) at −78° C. and underargon, a 1.5 M solution of diisobutylaluminium hydride in toluene (82.8mL, 124.2 mmol) in anhydrous tetrahydrofuran (150 mL) at −78° C. underan argon atmosphere was added dropwise via cannula. The solution wasstirred for six hours at this temperature and then diluted with ethylacetate (200 mL) and quenched with a saturated aqueous solution ofsodium tartrate (200 mL). The resulting mixture was stirred at roomtemperature overnight. The organic layer was separated, dried overmagnesium sulfate, filtrated and evaporated in vacuo. The residue waspurified by column chromatography using ethyl acetate and hexane 1:2 aseluent to afford 12.3 g (85% yield) of (2RS) and (2SR) ethyl(1SR,6RS,7SR)-2-hydroxy-3-oxa-bicyclo[4.1.0]heptane-7-carboxylate as acolorless oil, which exist with their corresponding open hydroxyaldehydeforms.

¹H-NMR (300 MHz, CDCl₃): 1.19-1.24 (m), 1.49-1.52 (m), 1.60-1.94 (m),2.00-2.08 (m), 2.30-2.34 (m), 2.53-2.58 (m), 3.25-3.30 (m), 3.34-3.50(m), 3.58-3.63 (m), 3.81-3.90 (m), 4.04-4.09 (m), 5.24 ((dd, J₁=5.5 Hz,J₂=4.4 Hz), 5.29 (d, J=3.3 Hz), 9.60 (dd, J₁=3.3 Hz, J₂=1.1 Hz),.

¹³C-NMR (75 MHz, CDCl₃): 13.9, 14.0, 14.1, 18.5, 20.6, 20.9, 21.0, 21.3,23.7, 25.0, 25.7, 27.3, 28.6, 28.7, 34.8, 54.2, 59.9, 60.5, 60.6, 61.1,61.6, 89.0, 90.0, 171.3, 173.3, 173.5 ppm.

d) (2SR) and(2RS)-2-(1′SR,2′SR,3′RS)-2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinonitrile

A suspension of ammonium chloride (29.3 g, 547.3 mmol) and neutralaluminium oxide (54.7 g) in acetonitrile (600 mL), was ultrasonicatedfor one hour. To this mixture, a solution of (2RS) and (2SR) ethyl(1SR,6RS,7SR)-2-hydroxy-3-oxa-bicyclo[4.1.0]heptane-7-carboxylate (10.2g, 54.7 mmol) in acetonitrile (200 mL) was added, and sonication wascontinued for an additional hour. Then, powdered potassium cyanide (42.8g, 656.7 mmol) was added and reaction mixture was ultrasonicated forseven days. After that time, the mixture was filtered through celite andthe inorganics washed with acetonitrile. The solvent was evaporatedunder reduced pressure to give a residue which contained a 1:1 racemicmixture of the two possible diastereomers. Both racemic aminonitrileswere purified and separated by column chromatography usingAcetone/Hexane 1:2 as eluent to give 3.89 g of(2SR,1′SR,2′SR,3′SR)-2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinonitrileand 3.67 g of(2RS,1′SR,2′SR,3′RS)-2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinonitrile.

e) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate

To a solution of(2SR,1′SR,2′SR,3′RS)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]-glycinonitrile (3.88 g, 18.3 mmol) in ethanol saturatedwith hydrogen chloride (200 mL) at 0° C., distilled water (0.99 mL, 54.9mmol) was added. The reaction was stirred at room temperature for fourdays. Then, solvent was eliminated in vacuo and residue dissolved inabsolute ethanol (100 mL), neutralized with NaHCO₃ (solid) and stirredfor 30 minutes. The inorganics were filtered and the solvent was removedunder reduced pressure to dryness. The resulting residue was taken intodioxan (150 mL), and a saturated aqueous solution of NaHCO₃ (50 mL) wasadded. To this mixture, a solution of di-tert-butyldicarbonate (4.80 mg,22.8 mmol) in dioxan (25 mL) was added and mixture stirred overnight atroom temperature. The layers were then separated and the aqueous layerwas extracted with ethyl acetate (2×200 mL). The combined organic layerswere dried over sodium sulfate, filtered and concentrated to dryness.The residue was purified by column chromatography using ethylacetate/hexane 1:2 as eluent to afford 3.34 g (56% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinateas a yellow oil.

¹H-NMR (300 MHz, CDCl₃): 1.25 (t, J=7.1 Hz, 3H), 1.30 (t, J=7.1 Hz, 3H),1.45 (s, 9H), 1.67-1.69 (m, 2H), 1.97-2.00 (m, 1H), 3.76-3.78 (m, 2H),4.04 (t, J=9.3 Hz, 1H), 4.11 (q, J=7.1 Hz, 2H), 4.23 (q, J=7.1 Hz, 2H),5.33 (d, J=8.2 Hz, 1H).

¹³C-NMR (75 MHz, CDCl₃): 14.0, 14.1, 24.3, 24.8, 28.2, 29.6, 30.9, 52.1,60.7, 61.7, 62.0, 80.1, 155.3, 171.4, 173.2 ppm.

f)(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-hydroxyethyl)-2′-carboxy)cyclopropyl]glycine

To a solution of ethyl(2SR,1′SR,2′SR,3′SR)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(100 mg, 0.28 mmol) in tetrahydrofuran (3.0 mL) at room temperature, a2.5N aqueous LiOH solution (4.5 mL, 11.2 mmol) was added. The mixturewas vigorously stirred overnight. The organic layer was separated anddiscarded and the aqueous layer was washed with diethylether. After theaqueous solution was adjusted to pH˜1 by addition of 1N HCl at 0° C., itwas extracted four times with AcOEt, and the combined organic layerswere dried over sodium sulfate and evaporated in vacuo. A solution ofthe residue in a IN solution of HCl in ethyl acetate (2.5 mL) wasstirred overnight. The solvent was then removed in vacuo and theresulting solid was washed with diethylether. The resultinghydrochloride salt of the title compound was dissolved in methanol (2.0mL) and propylene oxide (8.0 mL) was added. The mixture was stirredovernight and the resulting insoluble solid was filtered and washed withdiethylether to give the title compound (34 mg, 60%).

¹H-NMR (200 MHz, D₂O): 1.46-1.84 (m, 4H), 1.92-2.05 (m, 1H), 3.44 (d,J=10.5 Hz, 1H), 3.71 (br t, J=6.4 Hz, 2H).

¹³C-NMR (50 MHz, D₂C): 24.8, 25.7, 26.9, 29.8, 54.0, 60.9, 173.0, 178.0ppm.

a) Ethyl(2SR,1′RS,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(acetylthiomethyl)cyclopropyl]glycinate

To a solution of triphenylphosphine (152 mg, 0.58 mmol) in drytetrahydrofuran (1.8 mL) at 0° C. under argon, diethyl azodicarboxylate(0.091 mL, 0.58 mmol) was added dropwise. The mixture was stirred for 20min and then a solution of thioacetic acid (0.042 mL, 0.58 mmol) andethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(hydroxymethyl)cyclopropyl]glycinate(100 mg, 0.29 mmol) in dry tetrahydrofuran (0.9 mL) was added viacannula and stirred overnight at room temperature. Silicagel was addedto the mixture. The solvent was removed under reduced pressure and theresidue was purified by flash chromatography using hexane/ethyl acetate4:1 as eluent to give 70 mg of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(acetylthiomethyl)cyclopropyl]glycinate(60% yield).

¹H-NMR (200 MHz, CDCl₃) δ: 5.02 (bs, 1H); 4.21-3.98 (dc, 6H); 3.20 (m,1H); 3.00 (m, 1H); 2.27 (s, 3H); 1.74 (m, 1H); 1.38 (s, 9H) and 1.19(dt, 6H) ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 195.0; 172.2; 170.8; 155.1; 80.1; 61.8; 60.8;51.9; 30.8; 30.4; 27.9 (3C); 27.0; 25.2; 24.9 and 14.0 (2C) ppm.

b)(2SR,1′RS,2′RS,3′RS)-2-[3′-mercaptomethyl-2′-carboxycyclopropyl]glycine.

A solution of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(acetylthiomethyl)cyclopropyl]glycinate(240 mg, 0.59 mmol) in 6N HCl (5.3 mL) was heated under reflux for 16 h.The solvent was then removed in vacuo and the resulting solid was washedwith diethyl ether to give the corresponding hydrochloride salt of thetitle compound. After purification by ion exchange chromatography, 97 mg(80% yield) of(2SR,1′RS,2′RS,3′RS)-2-[3′-mercaptomethyl-2′-carboxycyclopropyl]glycinewere obtained as a white solid.

¹³C-NMR (50 MHz, D₂O/Py-d₅) δ: 178.1; 171.5; 52.7; 28.4; 27.2; 26.6 and21.7 ppm.

IR (film): 3437; 1631; 1385; 1234 and 889 cm⁻¹. Melting point: 200-202°C.

a) Ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(ethoxycarbonylmethylthiomethyl)cyclopropyl]glycinate.

To a solution of triphenylphosphine (388 mg, 1.48 mmol) in drytetrahydrofuran (4.5 mL) at 0° C. under argon, diethyl azodicarboxylate(0.233 mL, 1.48 mmol) was added dropwise. The mixture was stirred for 20min and then a solution of ethyl mercaptoacetate (0.133 mL, 1.48 mmol)and ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(hydroxymethyl)cyclopropyl]glycinate(256 mg, 0.74 mmol) in dry tetrahydrofuran (2.2 mL) was added viacannula and stirred overnight at room temperature. Silicagel was addedto the mixture. The solvent was removed under reduced pressure and theresidue was purified by flash chromatography using hexane/ethyl acetate4:1 as eluent to give 143 mg of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(ethoxycarbonylmethylthiomethyl)cyclopropyl]glycinate(43% yield).

¹H-NMR (200 MHz, CDCl₃) δ: 4.35 (d, 1H); 4.05 (m, 6H); 3.69 (s, 2H);3.61-3.53 (m, 3H); 2.30 (dd, 1H; J=3.0 and 7.3 Hz); 2.07 (m, 1H); 1.96(m, 1H); 1.35-1.13 (m, 18H) ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 171.6; 170.1; 169.6; 153.5; 80.1; 60.9; 60.6;60.2; 52.4; 49.1; 40.9; 29.7; 28.0; 25.2; 22.6 and 13.9 ppm.

IR (film): 2976, 2934, 1743, 1728, 1709, 1456, 1381, 1273, 1190, 1124,1041 and 958 cm⁻¹.

b) (2SR,1′RS,2′RS,3′RS)2-[3′-carboxymethylthiomethyl-2′-carboxycyclopropyl]glycinehydrochloride

A solution of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(ethoxy-carbonylmethylthiomethyl)cyclopropyl]glycinate(290 mg, 0.64 mmol) in 6N HCl (6 mL) was heated under reflux for 16 h.The solvent was then removed in vacuo and the resulting solid was washedwith diethyl ether to give 97 mg (52% yield) the correspondinghydrochloride salt of the title compound.

¹³C-NMR (50 MHz, MeOH-d₄) δ: 173.3; 173.0; 169.4; 61.9; 48.5; 41.9;28.1; 25.9 and 20.5 ppm.

IR (film): 3426; 3038; 2924; 1741; 1716; 1637; 1591; 1444; 1396; 1219and 1182 cm⁻¹.

a) Ethyl(2SR,1′RS,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(1H-tetrazol-5-ylthiomethyl)cyclopropyl]glycinate

To a solution of triphenylphosphine (1.32 g, 5.03 mmol) in drytetrahydrofuran (16 mL) at 0° C. under argon, diethyl azodicarboxylate(0.79 mL, 5.03 mmol) was added dropwise. The mixture was stirred for 20min and then a solution of 5-mercapto-1H-tetrazole (510 g, 5.03 mmol)and ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxy-carbonyl)-2-[2′-(ethoxycarbonyl)-3′-(hydroxymethyl)cyclopropyl]glycinate(870 mg, 2.52 mmol) in dry tetrahydrofuran (8 mL) was added via cannulaand stirred overnight at room temperature. Silicagel was added to themixture. Solvent was removed under reduced pressure and the residue waspurified by flash chromatography using a 5% solution of acetic acid inethyl acetate as eluent to give 430 mg of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(1H-tetrazol-5-ylthiomethyl)cyclopropyl]glycinate (40% yield).

¹H-NMR (200 MHz, CDCl₃) δ: 5.30 (bs, 1H); 4.48-4.01 (m, 5H); 3.63-3.53(dd, 1H); 3.44-3.33 (dd, 1H); 1.89-1.47 (m, 3H); 1.43 (s, 9H) and1.33-1.16 (dt, 6H) ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 173.0; 171.5; 156.7; 155.6; 80.2; 62.0; 61.4;52.5; 31.7; 30.1; 28.2 (3C); 27.2; 25.6; 14.1 and 13.9 ppm.

b)(2SR,1′RS,2′RS,3′RS)-2-[3′-(1H-tetrazol-5-yl-thiomethyl)-2′-carboxycyclopropyl]glycine

A solution of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(1H-tetrazol-5-yl-thiomethyl)cyclopropyl]glycinate(370 mg, 0.86 mmol) in 6N HCl (15 mL) was heated under reflux overnight.The solvent was then removed in vacuo and the resulting solid was washedwith diethylether to give the corresponding hydrochloride salt of thetitle compound. After purification by ion exchange chromatography, 140mg (60% yield) of(2SR,1′RS,2′RS,3′RS)-2-[3′-(1H-tetrazol-5-yl-thiomethyl)-2′-carboxycyclopropyl]glycinewere obtained as a white solid.

¹H-NMR (200 MHz, D₂O/KOD) δ: 3.37-3.28 (dd, 1H); 3.01-2.82 (m, 2H);1.62-1.43 (m, 2H) and 1.25 (t, 1H) ppm.

¹³C-NMR (50 MHz, D₂O/KOD) δ: 181.6; 181.3; 158.3; 55.7; 32.8; 32.2; 29.1and 26.0 ppm.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-acetylthioethyl)cyclopropyl]glycinate

To a solution of triphenylphosphine (309 mg, 1.18 mmol) in drytetrahydrofuran (3 mL) at 0° C. under argon, diethyl azodicarboxylate(0.185 mL, 1.18 mmol) was added dropwise. The mixture was stirred for 20min and then a solution of thioacetic acid (0.091 mL, 1.18 mmol) andethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(212 mg, 0.59 mmol) in dry tetrahydrofuran (6 mL) was added via cannulaand stirred overnight at room temperature. Silicagel was added to themixture. The solvent was removed under reduced pressure and the residuewas purified by flash chromatography using hexane and ethyl acetate 3:1as eluent to give 123 mg of ethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-acetylthioethyl)cyclopropyl]glycinate(50% yield).

¹H-NMR (200 MHz, CDCl₃) δ: 5.20 (bs, 1H); 4.26-4.04((m, 4H); 3.94 (bs,1H); 3.04-2.96 (m, 2H); 2.30 (s, 3H); 1.73-1.58 (m, 5H); 1.42 (s, 9H)and 1.31-1.21 (m, 6H) ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 195.2; 172.8; 171.1; 155.2; 80.1; 61.6; 60.6;52.1; 30.8; 30.5; 29.8; 29.3; 28.1 (3C); 26.7; 25.6; 14.1 and 14.0 ppm.

b) (2SR,1′SR,2′SR,3′RS)2-[3′-(2″-mercaptoethyl)-2′-carboxycyclopropyl]glycine

A solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-acetylthioethyl)cyclopropyl]glycinate(123 mg, 0.29 mmol) in 6N HCl (2.5 mL) was heated under reflux for 17 h.The solvent was then removed in vacuo and the resulting solid was washedwith diethylether to give the corresponding hydrochloride salt of thetitle compound. After purification by ion exchange chromatography, 48 mg(74% yield) of(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-mercaptoethyl)-2′-carboxycyclopropyl]glycinewere obtained as a white solid.

¹³C-NMR (50 MHz, D₂O/KOD) δ: 182.7; 181.7; 55.9; 37.7; 31.4; 28.6; 27.3and 25.5 ppm.

a) Ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(methylthiomethyl)cyclopropyl]glycinate

A mixture of tributylphosphine (1.16 mL, 4.72 mmol), dimethyl disulfide(0.31 mL, 3.54 mmol) and ethyl (2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(hydroxymethyl)cyclopropyl]glycinate(410 mg, 1.18 mmol) in dry tetrahydrofuran (8 mL), was stirred at 50° C.under argon for 20 h. Then, silicagel was added to the mixture andsolvent was removed under reduced pressure. The resulting residue waspurified by flash chromatography using hexane and diethylether 7:3 aseluent to afford 45 mg (10% yield) of the title compound.

¹H-NMR (200 MHz, CDCl₃) δ: 5.30 (bd, 1H); 4.25-3.93 (m, 5H); 2.90 (m,1H); 2.49 (m, 1H); 2.12 (s, 3H); 1.76 (m, 3H); 1.40 (s, 9H) and1.29-1.12 (m, 6H) ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 172.4; 171.0; 155.2; 80.1; 62.1; 61.7; 52.0;32.4; 29.9; 28.2 (3C); 27.3; 25.7; 15.5 and 14.5 (2C) ppm.

b)(2SR,1′RS,2′RS,3′RS)-2-[3′-(methylthiomethyl)-2′-carboxycyclopropyl]glycine

A solution of ethyl (2SR,1′RS,2′RS,3′RS) N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(methylthiomethyl)cyclopropyl]glycinate (55mg, 0.14 mmol) in 6N HCl (2.5 mL) was heated under reflux for 16 h. Thesolvent was then removed in vacuo and the resulting solid was washedwith diethyl ether to give the corresponding hydrochloride salt of thetitle compound. After purification by ion exchange chromatography, 26 mg(80% yield) of (2SR,1′RS,2′RS,3′RS)-2-[3′-(methylthiomethyl)-2′-carboxycyclopropyl]glycine wereobtained as a white solid.

¹H-NMR (200 MHz, D₂O/Py-d₅) δ: 3.07 (d, 1H, J=10 Hz); 2.60 (m, 1H); 1.88(m, 1H); 1.45 (d, 5H) and 1.53 (t, 1H) ppm.

¹³C-NMR (50 MHz, D₂O/Py-d₅) δ: 179.1; 172.6; 54.2; 31.6; 29.6; 26.3;25.7 and 13.7 ppm.

a) Ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(phenylthiomethyl)cyclopropyl]glycinate

A mixture of tributylphosphine (0.26 mL, 1.04 mmol) , diphenyl disulfide(170 mg, 0.78 mmol) and ethyl (2SR,1′SR,2′RS,3′-RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(hydroxymethyl)cyclopropyl]glycinate (90 mg, 0.26 mmol) in dry tetrahydrofuran (2 mL),was stirred at room temperature under argon for 20 h. Then, silicagelwas added to the mixture and solvent was removed under reduced pressure.The resulting residue was purified by flash chromatography using hexaneand ethyl acetate 4:1 as eluent to afford 80 mg (70% yield) of the titlecompound.

¹H-NMR (200 MHz, CDCl₃) δ: 7.25 (m, 5H); 5.20 (bd, 1H); 4.10 (m, 5H);3.30 (dd, 1H); 2.85 (m, 1H); 1.75 (m, 3H); 1.40 (s, 9H) and 1.25 (m, 6H)ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 172.3; 170.9; 155.2; 135.2; 130.5; 128.9;126.6; 80.2; 61.7; 60.7; 52.1; 33.3; 30.2; 28.1 (3C); 26.9; 25.7 and14.0 ppm.

IR (film): 3343, 3063, 2904, 1747, 1701, 1684, 1522, 1454, 1367, 1332,1174, 1030 and 734 cm⁻¹.

Melting point: 90.0-92.5° C.

b)(2SR,1′RS,2′RS,3′RS)-2-[3′-(phenylthiomethyl)-2′-carboxycyclopropyl]glycine

A solution of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(phenylthiomethyl)cyclopropyl]glycinate (77 mg, 0.17 mmol) in 6N HCl (3 mL) was heated under refluxfor 16 h. The solvent was then removed in vacuo and the resulting solidwas washed with diethyl ether to give the corresponding hydrochloridesalt of the title compound. After purification by ion exchangechromatography, 41 mg (83% yield) of (2SR,1′RS,2′RS,3′RS)-2-[3′-(phenylthiomethyl)-2′-carboxycyclopropyl]glycine wereobtained as a white solid.

¹H-NMR (200 MHz, D₂O/Py-d₅) δ: 6.99-6.47 (m, 5H); 3.11-3.01 (m, 2H),2.32-2.21 (m, 1H); 1.57-1.41 (m, 2H) and 1.24-1.19 (t, 1H) ppm.

¹³C-NMR (50 MHz, D₂O/Py-d₅) δ: 179.3; 173.0; 135.4; 129.6; 129.4; 126.3;54.9; 32.9; 29.4; 27.7 and 25.8 ppm.

IR (film): 3059, 1716, 1678, 1585, 1514, 1385, 1184, 1014 and 897 cm⁻¹.

Melting point: 201° C.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-phenylthioethyl)cyclopropyl]glycinate

A mixture of tributylphosphine (0.52 mL, 2.12 mmol), diphenyl disulfide(346 mg, 1.58 mmol) and ethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(190 mg, 0.53 mmol) in dry tetrahydrofuran (5.5 mL), was stirred at roomtemperature under argon for 20 h. Then, silicagel was added to themixture and solvent was removed under reduced pressure. The resultingresidue was purified by flash chromatography using hexane and ethylacetate 4:1 as eluent to afford 186 mg (78% yield) of the titlecompound.

¹H-NMR (200 MHz, CDCl₃) δ: 7.32-7 30 (m, 5H); 5.20 (bd, 1H); 4.23-4.04(m, 4H); 3.90 (bs, 1H); 3.06 (t, 2H); 2.06 (m, 1H); 1.71-1.66 (m, 4H);1.43 (s, 9H) and 1.27 (m, 6H) ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 172.8; 171.1; 155.2; 136.1; 130.6; 129.3;128.0; 126.0; 80.1; 61.6; 60.7; 52.1; 33.1; 30.1; 28.1 (3C); 27.8; 26.8;25.5; 14.1 and 13.9 ppm.

b)(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-phenylthioethyl)-2′-carboxycyclopropyl]glycine

A solution of ethyl (2SR,1′SR,2′SR,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-phenylthioethyl)cyclopropyl]glycinate(186 mg, 0.41 mmol) in 6N HCl (3.3 mL) was heated under refluxovernight. The solvent was then removed in vacuo and the resulting solidwas washed with diethyl ether to give the corresponding hydrochloridesalt of the title compound. After purification by ion exchangechromatography, 60 mg (49% yield) of(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-phenylthioethyl)-2′-carboxycyclopropyl]glycinewere obtained as a white solid.

¹H-NMR (200 MHz, D₂O/Py-d₅) δ: 6.56-6.44 (m, 5H); 2.95 (d, 1H),2.50-2.36 (m, 2H); 1.53 (m, 2H); 1.30 (m, 1H); 1.14 (m, 1H) and 1.05 (m,1H) ppm.

¹³C-NMR (50 MHz, D₂O/Py-d₅) δ: 179.0; 171.7; 136.2; 128.5; 127.7; 125.1;123.4; 54.5; 31.7; 28.0; 27.4; 26.8 and 25.5 ppm.

IR (film): 3132, 3020, 2955, 2914, 1730, 1626, 1529, 1481, 1387, 1358,1329, 1219 and 746 cm⁻¹.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-benzylthioethyl)cyclopropyl]glycinate

To a mixture of tributylphosphine (0.70 mL, 2.83 mmol), dibenzyldisulfide (522 mg, 2.12 mmol) and ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(254 mg, 0.71 mmol) in dry tetrahydrofuran (7 mL),N,N-dimethylamino-pyridine g(8.5 mg, 0.07 mmol) was added and thereaction mixture was stirred at 75° C. under argon for 24 h. Then,silica gel was added to the mixture and solvent was removed underreduced pressure. The resulting residue was purified by flashchromatography using hexane and ethyl acetate 3:1 as eluent to afford 59mg (18% yield) of the title compound.

¹H-NMR (200 MHz, CDCl₃) δ: 7.32-7.26 (m, 5H); 5.19 (bd, 1H); 4.26-4.13(m, 5H); 4.12 (m, 1H); 3.88 (m, 1H); 2.55 (t, 2H); 2.16 (s, 2H);1.99-1.87 (m,1H); 1.84(m,1H); 1.69 (m,1H); 1.45 (s, 9H) and 1.25 (m, 6H)ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 172.9; 171.1; 155.2; 138.2; 129.2; 128.8;128.4; 126.9; 80.1; 61.6; 60.6; 52.1; 36.3; 30.1; 29.6; 29.3; 28.2; 28.0(3C); 27.0 and 14.0 ppm.

b)(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-benzylthioethyl)-2′-carboxycyclopropyl]glycinehydrochloride

A solution of ethyl (2SR,1′SR,2′SR,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-benzylthioethyl)cyclopropyl]glycinate(71 mg, 0.15 mmol) in 2N HCl (3.7 mL) was heated under reflux overnight.The solvent was then removed in vacuo and the resulting solid was washedwith diethyl ether to give 41 mg (77% yield) of(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-benzylthioethyl)-2′-carboxycyclopropyl]glycinehydrochloride as a white solid.

¹H-NMR (200 MHz, CD₃OD) δ: 7.34-7.20 (m, 5H); 3.75 (s, 2H); 3.64 (d,1H); 2 61 (t, 2H), 2.12 (m, 1H) and 1.84-1.50 (m, 4H) ppm.

¹³C-NMR (50 MHz, CD₃OD) δ: 175.4; 170.6; 140.0; 129.9; 129.4; 127.9;53.3; 37.0; 31.5; 28.9; 28.2; 27.7 and 26.1 ppm.

a) Ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(methylsulfonylmethyl)cyclopropyl]glycinate

To a solution of ethyl (2 SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(methylthiomethyl)cyclopropyl]glycinate(54 mg, 0.14 mmol) in anhydrous dichloromethane (1 mL) at 0° C. under anitrogen atmosphere, m-chloroperoxybenzoic acid (71 mg, 0.28 mmol) wasadded. The mixture was stirred for 1 h at this temperature. Then, theresidue was diluted with dichloromethane and washed with a 15% aqueoussolution of sodium bisulfite and with a saturated aqueous solution ofsodium bicarbonate. The organic phase was dried over magnesium sulfate,and the solvent removed under reduced pressure. The residue was purifiedby flash chromatography using hexane and ethyl acetate 1:1 as eluent toafford 42 mg (72% yield) of the title compound.

¹H-NMR (200 MHz, CDCl₃) δ: 5.33 (bd, 1H, J=8.4 Hz); 4.27-4.06 (dq, 4H);3.93 (t, 1H, J=8.9 Hz); 3.56-3.48 (dd, 1H, J=3.2 and 14.7 Hz); 3.03 (m,1H); 2.93 (s, 3H); 2.04-1.78 (m, 3H); 1.40 (s, 9H) and 1.31-1.18 (dt,6H) ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 171.2; 170.4; 155.3; 80.4; 62.2; 61.5; 53.7;52.0; 40.3; 28.1 (3C); 27.7; 24.9 and 19.0 ppm.

b)(2SR,1′RS,2′RS,3′RS)-2-[3′-(methylsulfonylmethyl)-2′-carboxycyclopropyl]glycine

A solution of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(methylsulfonylmethyl)cyclopropyl]glycinate(42 mg, 0.10 mmol) in 6N HCl (2 mL) was heated under reflux for 16 h.The solvent was then removed in vacuo and the resulting solid was washedwith diethylether to give the corresponding hydrochloride salt of thetitle compound. This hydrochloride was dissolved in MeOH (1 mL) andpropylene oxide (3 mL) was added. The mixture was stirred overnight atroom temperature and the resulting insoluble solid was filtered andwashed with diethylether to give 19 mg (74% yield) of(2SR,1′RS,2′RS,3′RS)-2-[3′-(methylsulfonylmethyl)-2′-carboxycyclopropyl]-glycineas a white solid.

¹H-NMR (200 MHz, D₂O/Py-d₅) δ: 3.45(d, 1H); 3.10-2.50 (m, 3H); 2.54 (s,3H) and 1.58 (bs, 2H) ppm.

¹³C-NMR (50 MHz, D₂O/Py-d₅) δ: 178.2; 172.6; 54.7; 53.8; 39.7; 28.7;25.0 and 19.0 ppm.

a) Ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(phenylsulfonylmethyl)cyclopropyl]glycinate

To a solution of ethyl (2 SR,1′RS,2′ RS,3′ RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(phenylthiomethyl)cyclopropyl]glycinate(50 mg, 0.11 mmol) in anhydrous dichloromethane (1 mL) at 0° C. undernitrogen atmosphere, m-chloroperoxybenzoic acid (54.3 mg, 0.22 mmol) wasadded. The mixture was stirred for 3h at this temperature. Then, theresidue was diluted with dichloromethane and washed with a 15% aqueoussolution of sodium bisulfite and with a saturated aqueous solution ofsodium bicarbonate. The organic phase was dried over magnesium sulfate,and the solvent removed under reduced pressure. The residue was purifiedby flash chromatography using hexane and ethyl acetate 2:1 as eluent toafford 42 mg (78% yield) the title compound.

¹H-NMR (200 MHz, CDCl₃) δ: 8.33 (d, 2H, J=6 Hz); 8.11-7.80 (m, 3H);5.27(bd, 1H, J=8 Hz); 4.31-4.04 (dq, 4H); 3.88 (t, 1H); 3.78-3.69 (dd,1H); 3.08 (m, 1H); 1.84-1.59 (m,3H); 1.44 (s, 9H) and 1.36-1.22 (dt, 6H)ppm.

¹³C-NMR (50 MHz, CDCl₃) δ: 171.3; 170.4; 155.1; 138.4; 133.9; 129.3;128.3; 80.5; 62.0; 61.8; 55.2; 52.0; 28.1 (3C); 27.9; 24.9; 20.0 and14.1 (2C) ppm.

IR (film): 3408, 3358, 2982, 1736, 1724, 1697, 1512, 1371, 1294, 1250,1178, 1145, 1086 and 1020 cm⁻¹.

Melting point: 101-102° C.

b)(2SR,1′RS,2′RS,3′RS)-2-[3′-(phenylsulfonylmethyl)-2′-carboxycyclopropyl]glycine

A solution of ethyl (2SR,1′RS,2′RS,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(phenylsulfonylmethyl)cyclopropyl]glycinate (60 mg, 0.12 mmol) in 6N HCl (2 mL) was heated under refluxfor 16 h. The solvent was then removed in vacuo and the resulting solidwas washed with diethylether to give the corresponding hydrochloridesalt of the title compound. After purification by ion exchangechromatography, 24 mg (60% yield) of(2SR,1′RS,2′RS,3′RS)-2-[3′-(phenylsulfonylmethyl)-2′-carboxycyclopropyl]glycinewere obtained as a white solid.

¹H-NMR (200 MHz, D₂O/Py-d₅) δ: 7.40 (d, 2H); 7.15(m, 3H); 3.65 (d, 1H);3.45(m, 1H); 2.90(m, 1H) and 1.40(m, 3H) ppm.

¹³C-NMR (50 MHz, D₂O/Py-d₅) δ: 178.1; 172.7; 136.6; 134.7; 129.8; 128.1;55.3; 54.7; 28.6; 25.0 and 19.3 ppm.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(azidomethyl)cyclopropyl]glycinate

Diethyl azodicarboxylate (1.08 mmol, 0.17 mL) was added dropwise to asolution of triphenylphosphine (1.08 mmol, 0.285 g) in anhydroustetrahydrofuran (20 mL) at 20° C. under a nitrogen atmosphere and thereaction mixture was stirred at the same temperature for 10 min. Asolution of ethyl(2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxy-methylcyclopropyl]glycinate(0.87 mmol, 300 mg) in tetrahydrofuran (5 mL) was then added and theresulting mixture stirred for 10 min at −20° C. After that time,diphenylphosphoryl azide (1.13 mmol, 0.25 mL) was added to the reactionmixture at the same temperature and then allowed to react at roomtemperature for 3 days. The reaction mixture was quenched with water andthe organic phase extracted with ethyl acetate (2×25 mL). The combinedorganic layers were dried over magnesium sulfate, filtered andconcentrated under vacuo. The product was purified by columnchromatography using hexane and ethyl acetate 4:1 as eluent to give 250mg (78% yield) of ethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(azidomethyl)-cyclopropyl]glycinate as a colorless oil.

1H-NMR (CDCl₃, 200 MHz) δ ppm): 5.2 (1H, d, J=8 Hz), 4.3-3.9 (5H, m),3.6 (1H, dd, J=13 and 5 Hz), 3.3 (1H, dd, J=13 and 7 Hz), 1.9-1.7 (3H,m), 1.4 (9H, s), 1.3-1.2 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 172.1, 170.7, 155.2, 80.2, 61.8, 61.0,52.0, 49.4, 29.0, 28.1, 25.4, 24.0, 14.0

b) (2SR,1′SR,2′SR,3′RS)-2-(3′-azidomethyl-2′-carboxycyclopropyl)glycine

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-azidomethylcyclopropyl]glycinate(75 mg, 0.20 mmol) in tetrahydrofuran (2 mL) at room temperature, a 2.5Msolution of LiOH.H₂O in H₂O (3.2 mL, 8 mmol) was added and mixture wasstirred at room temperature overnight. The following day, ethyl acetatewas added, organic layer separated and aqueous layer washed with ethylacetate (2×). The aqueous layer was acidified to pH 1 with 1N HCl andextracted in ethyl acetate (5×). The combined organic layers were driedover magnesium sulfate, filtered and concentrated under reducedpressure. The resulting residue was dissolved in a 1N solution of HCl inethyl acetate (1.6 mL) and the solution was stirred overnight at roomtemperature. Then, it was concentrated under vacuum and the solid waswashed with diethyl ether. The resulting hydrochloride salt of the titlecompound was dissolved in methanol (2 mL) and propylene oxide (5 mL) wasadded. The mixture was stirred overnight and the precipitate wasfiltered and washed with diethyl ether to give 32 mg (73% yield) of(2SR,1′SR,2′SR,3′RS)-2-(3′-azidomethyl-2′-carboxycyclopropyl)glycine asa white solid.

¹H-NMR (D₂O, 200 MHz) δ ppm): 3.6 (1H, dd, J=13, 5 Hz), 3.3 (1H, d, J=10Hz), 3.2 (1H, dd, J=13, 8 Hz), 1.9-1.7 (3H, m)

¹³C-NMR (D₂O/MeOH-d₄, 50 MHz) δ ppm): 177.4, 173.2, 54.7, 50.1, 27.4,26.9, 25.7

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-fluoroethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate (0.84 mmol, 300 mg) in dichloromethane (15 mL) at roomtemperature, (diethylamino)sulfur trifluoride (1.26 mmol, 0.17 mL) wasadded. The resulting mixture was stirred for 1.5 h and then quenchedwith water (5 mL). The layers were separated and the aqueous phase wasextracted with dichloromethane (3×10 mL). The combined organic layerswere dried over magnesium sulfate, filtered and concentrated undervacuum. The product was purified by column chromatography using a hexaneand ethyl acetate 4:1 as eluent to afford 160 mg (53% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-fluoroethyl)cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ ppm): 5.3 (1H, d, J=7 Hz), 4.7-4.4 (2H, dt,J=47, 6 Hz), 4.2 (2H, q, J=7 Hz), 4.1 (2H, q, J=7 Hz), 3.9 (1H, m),2.3-1.7 (5H, m), 1.4 (9H, s), 1.3-1.2 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 172.7, 171.0, 155.2, 82.8 (d, J=167 Hz),80.1, 61.6, 60.6, 52.1, 29.2 (d, J=14 Hz), 28.7, 28.1, 24.4, 23.7 (d,J=7 Hz), 14.0, 13.9

b)(2SR,1′SR,2′SR,3′RS)-2-(3′-(2″-fluoroethyl)-2′-carboxycyclopropyl)glycine

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-fluoroethyl)cyclopropyl]glycinate(150 mg, 0.41 mmol) in tetrahydrofuran (4.1 mL), a 2.5M solution ofLiOH.H₂O (340 mg, 8.2 mmol) in H₂O (3.4 mL) was added and the mixturewas stirred at room temperature overnight. The following day, ethylacetate (2 mL) was added, organic layer separated and aqueous layerwashed with ethyl acetate (3×2 mL). The aqueous layer was acidified topH 1 with 1N HCl and extracted in ethyl acetate (5×10 mL). The combinedorganic layers were dried over magnesium sulfate, filtered andconcentrated under vacuum. The residue was dissolved in a 1N solution ofHCl in ethyl acetate (3.3 mL, 3.3 mmol) and the solution was stirredovernight at room temperature. It was concentrated under vacuum and thesolid was washed with diethyl ether to give the correspondinghydrochloride salt of the title compound. After purification by ionexchange chromatography, 70 mg (83% yield) of(2SR,1′SR,2′SR,3′RS)-2-(3′-(2″-fluoroethyl)-2′-carboxycyclopropyl)glycine were obtained as a white solid.

¹H-NMR (D₂O, 200 MHz) δ ppm): 4.5-4.3 (2H, dt, J=47, 5 Hz), 3.3 (1H, d,J=10 Hz), 2.2-1.9 (1H, m), 1.7-1.3 (4H, m)

¹³C-NMR (D₂O/py-d₅, 50 MHz) δ ppm): 180.4, 173.2, 147.0, 84.3 (d, J=160Hz), 54.6, 28.5 (d, J=15 Hz), 27.9, 25.8, 22.7 (d, J=5 Hz).

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-chloroethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(0.84 mmol, 300 mg) in anhydrous dimethylformamide (6 mL),triphenylphosphine (2.5 mmol, 0.65 g) and carbon tetrachloride (6 mL)were added at room temperature. The resulting mixture was stirredovernight and then water (3 mL) and ethyl acetate (20 mL) were added.The organic layer was separated and the aqueous layer was extracted withethyl acetate (3×10 mL). The combined organic layers were washed withwater (5×10 mL), dried over magnesium sulfate, filtered and concentratedunder vacuum. The residue was purified by column chromatography usinghexane and ethyl acetate 4:1 as eluent to afford 220 mg (58% yield) ofethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-chloroethyl)cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ ppm): 5.3 (1H, d, J=8 Hz), 4.2 (2H, d, J=7Hz), 4.1 (2H, d, J=7 Hz), 3.9 (1H, m), 3.6 (2H, t, J=6 Hz), 2.3-2.1 (1H,m), 1.9-1.6 (4H, m), 1.4 (9H, s), 1.3-1.2 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 172.6, 170.9, 155.2, 80.0, 61.6, 60.6,52.1, 43.6, 31.0, 29.5, 27.7, 25.1, 24.5, 14.0, 13.9

b) Synthesis of(2SR,1′SR,2′SR,3′RS)-2-(3′-(2″-chloroethyl)-2′-carboxycyclopropyl)glycinehydrochloride

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-chloroethyl)cyclopropyl]glycinate(200 mg, 0.53 mmol) in tetrahydrofuran (5.3 mL), a 0.25 M solution ofLiOH.H₂O (66 mg, 1.59 mmol) in H₂O (6.4 mL) was added and the mixturewas stirred at room temperature for three days. Then, ethyl acetate (3mL) was added, the organic layer was separated and the aqueous layer waswashed with ethyl acetate (3×3 mL). The aqueous layer was acidified topH 1 with 1N HCl and extracted in ethyl acetate (5×10 mL). The combinedorganic layers were dried over magnesium sulfate, filtered andconcentrated under vacuum. The residue was dissolved in a 1N solution ofHCl in EtOAc (4.2 mL, 4.2 mmol) and the solution was stirred overnightat room temperature. The resulting mixture was concentrated under vacuumand the solid was washed with diethyl ether to give the correspondinghydrochloride salt of the title compound. After purification by ionexchange chromatography, 80 mg (68% yield) of (2SR,1′SR,2′SR,3′RS)-2-(3′-(2″-chloroethyl)-2′-carboxy cyclopropyl)glycine wereobtained as a white solid.

¹H-NMR (D₂O, 200 MHz) δ ppm): 3.5 (2H, t, J=10 Hz), 3.3 (1H, d, J=10Hz), 2.1-1.9 (1H, m), 1.7-1.3 (4H, m).

¹³C-NMR (D₂O/py-d₅, 50 MHz) δ ppm): 179.3, 172.7, 54.5, 44.2, 30.6,27.8, 26.1, 23.9.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(acetylaminomethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(azidomethyl)cyclopropyl]glycinate(500 mg, 1.35 mmol) in ethanol (15 mL), acetic anhydride (0.3 mL, 2.7mmol) and 10% palladium on activated carbon (90 mg) were added. Theresulting mixture was stirred at room temperature under hydrogenatmosphere for 2 hours. Then, mixture was filtered through celite andconcentrated under reduced pressure. The resulting residue was purifiedby column chromatography using hexane and ethyl acetate 1:1 as eluent toafford 375 mg (72% yield) of ethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-31-(acetylaminomethyl)cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ ppm): 6.6 (1H, broad s), 5.3 (1H, d, J=8 Hz),4.3-3.9 (6H, m), 2.9-2.8 (1H, m), 1.9 (3H, s), 1.9-1.7 (3H, m), 1.4 (9H,s), 1.3-1.1 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 172.1, 171.6, 169.9, 155.5, 80.4, 62.1,60.9, 52.4, 37.7, 28.9, 28.1, 26.6, 23.2, 14.0.

b)(2SR,1′SR,2′SR,3′RS)-2-(3′-acetylaminomethyl-2′-carboxycyclopropyl)glycine

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(acetyl-aminomethyl)cyclopropyl]glycinate (60 mg, 0.15 mmol) in tetrahydrofuran (1.5 mL), a 2.5Msolution of LiOH.H₂O (252 mg, 6.0 mmol) in H₂O (2.4 mL) was added andthe mixture was stirred at room temperature overnight. The following dayethyl acetate (1 mL) was added, the organic layer was separated and theaqueous layer was washed with ethyl acetate (3×1 mL). The aqueous layerwas acidified to pH 1 with 1N HCl and extracted with ethyl acetate (5×5mL). The combined organic layers were dried over magnesium sulfate,filtered and concentrated under vacuum. The residue was dissolved in a1N solution of HCl in ethyl acetate (1.75 mL, 1.75 mmol) and thesolution was stirred overnight at room temperature. It was concentratedunder vacuum and the solid was washed with diethyl ether to give thecorresponding hydrochloride salt of the title compound. Thishydrochloride was dissolved in MeOH (1 mL) and propylene oxide (3 mL)was added. The mixture was stirred overnight at room temperature and theresulting insoluble solid was filtered and washed with diethyl ether togive 10 mg of(2SR,1′SR,2′SR,3′RS)-2-(3′-acetylaminomethyl-2′-carboxycyclopropyl)glycine(30% yield) as a white solid.

¹H-NMR (D₂O/MeOH-d₄, 200 MHz) δ ppm): 3.7 (1H, dd, J=14, 6 Hz), 3.2 (1H,d, J=10 Hz), 3.0 (1H, dd, J=14, 7 Hz), 1.9 (3H, s), 1.8-1.6 (3H, m)

¹³ C-NMR (D₂O/MeOH-d₄, 50 MHz) δ ppm): 175.4, 172.3, 171.4, 52.8, 36.9,26.0, 25.2, 23.5, 21.0

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(benzoylaminomethyl)-cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(azidomethyl)cyclopropyl]glycinate(500 mg, 1.35 mmol) in ethyl acetate (15 mL), benzoic anhydride (0.23mL, 2.0 mmol) and platinium (IV) oxide (61 mg, 0.27 mmol) were added.The resulting mixture was stirred at room temperature under hydrogenatmosphere for 2 hours. Then, the mixture was filtered through celiteand concentrated under reduced pressure. The resulting residue waspurified by column chromatography using hexane and ethyl acetate 1:1 aseluent to afford 363 mg (65% yield) of ethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-31-(benzoylaminomethyl)cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ ppm): 7.9 (2H, m), 7.6-7.4 (3H, m), 5.3 (1H,d, J=8 Hz), 4.5 (1H, m), 4.4-4.1 (5H, m), 3.1-3.0 (1H, m), 2.0-1.8 (3H,m), 1.5 (9H, s), 1.3-1.2 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 172.1, 171.7, 167.0, 155.4, 134.2,131.3, 128.4, 127.0, 80.5, 62.4, 61.0, 52.5, 38.0, 28.9, 28.2, 26.6,23.0, 14.0

b)(2SR,1′SR,2′SR,3′RS)-2-(3′-benzoylaminomethyl-2′-carboxycyclopropyl)glycine

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(benzoylaminomethyl)cyclopropyl]glycinate (50 mg, 0.11 mmol) in tetrahydrofuran (1.5 mL), a 2.5Msolution of LiOH.H₂O (185 mg, 4.4 mmol) in H₂O (1.75 mL) was added andthe mixture was stirred at room temperature overnight. The following dayethyl acetate (1 mL) was added, the organic layer separated and theaqueous layer was washed with ethyl acetate (3×1 mL). The aqueous layerwas acidified to pH 1 with 1N HCl and extracted with ethyl acetate (5×3mL). The combined organic layers were dried over magnesium sulfate,filtered and concentrated under vacuum. The residue was dissolved in a1N solution of HCl in ethyl acetate (1 mL, 1 mmol) and the solution wasstirred overnight at room temperature. It was then concentrated undervacuum and the solid was washed with diethyl ether to give thecorresponding hydrochloride salt of the title compound. Afterpurification by ion exchange chromatography, 8.0 mg (25% yield) of(2SR,1′SR,2′SR, 3′RS)-2-(3′-benzoylaminomethyl-2′-carboxycyclopropyl)glycine were obtained as a white solid.

¹H-NMR (D₂O/py-d₅, 200 MHz) δ ppm): 7.6-7.1 (5H, m), 3.8 (1H, dd, J=14,5 Hz), 3.3 (1H, d, J=10 Hz), 2.7 (1H, dd, J=14, 8 Hz), 1.7-1.5 (3H, m)

¹³C-NMR (D₂O/py-d₅, 50 MHz) δ ppm): 179.7, 173.3, 169.1, 133.2, 132.2,128.8, 127.3, 54.6, 38.8, 27.1, 26.4, 25.0

a) (2SR,1′SR,2′SR,3′RS)-2-[3′-aminomethyl-2′-carboxycyclopropyl]glycine

A solution of ethyl(2SR,1SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3-(acetylaminomethyl)cyclopropyl]glycinate(300 mg, 0.77 mmol) in 2N HCl (5 mL) was stirred at room temperature for24 hours and then heated at 55²C for 60 hours. Solvent was removed undervacuum to give the corresponding hydrochloride salt of the titlecompound. After purification by ion exchange chromatography, 58 mg (40%yield) of (2SR,1′SR,2′SR, 3′RS)-2-(3′-aminomethyl-2′-carboxycyclopropyl)glycine were obtained as a white solid.

¹H-NMR (D₂O/py-d₅, 200 MHz) δ ppm): 3.3 (1H, m), 3.3 (1H, d, J=11 Hz),2.7 (1H, dd, J=13, 10 Hz), 1.8-1.5 (3H, m)

¹³C-NMR (D₂O/py-d₅, 50 MHz) 8ppm): 178.3, 172.7, 53.8, 38.2, 27.0, 25.6,21.8

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(benzylcarbonylaminomethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(azidomethyl)cyclopropyl]glycinate (100 mg, 0.27 mmol) in ethyl acetate (4 mL),platinum (IV) oxide (0.054 mmol, 12 mg) was added and the mixture wasallowed to react at room temperature under a hydrogen atmosphere for 4hours. Then, the phenylacetyl chloride (0.072 mL, 0.54 mmol) was addedand the reaction mixture was stirred at room temperature under nitrogenatmosphere overnight. The following day, the mixture was filteredthrough celite and concentrated under vacuum. The residue was purifiedby column chromatography using a gradient from hexane and ethyl acetate6:4 to ethyl acetate as eluent to afford 55 mg (45% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(benzylcarbonylaminomethyl)cyclopropyl]-glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ ppm): 7.3 (5H, m), 6.6 (1H, broad s), 5.4 (1H,broad s), 4.2-3.9 (5H, m), 3.5 (3H, s), 1.8-1.7 (3H, m), 1.4 (9H, s),1.3-1.2 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 174.2, 172.2, 171.3, 155.3, 134.8,129.2, 128.7, 127.0, 80.3, 62.4, 61.2, 52.4, 43.6, 37.8, 28.9, 28.1,26.5, 23.1, 14.0

b)(2SR,1′SR,2′SR,3′RS)-2-(3′-benzylcarbonylaminomethyl-2′-carboxycyclopropyl)glycine

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(benzylcarbonyl-aminomethyl)cyclopropyl]glycinate(221 mg, 0.48 mmol) in tetrahydrofuran (5 mL), a 2.5M solution ofLiOH.H₂O (806 mg, 19.2 mmol) in H₂O (7.7 mL) was added and the mixturewas stirred at room temperature overnight. The following day ethylacetate (3 mL) was added, the organic layer was separated and theaqueous layer was washed with ethyl acetate (3×3 mL). The aqueous layerwas acidified to pH 1 with 1N HCl and extracted into ethyl acetate (5×10mL). The combined organic layers were dried over magnesium sulfate,filtered and concentrated under vacuum. The residue was dissolved in a1N solution of HCl in ethyl acetate (2.2 mL, 2.2 mmol) and the solutionwas stirred overnight at room temperature. It was concentrated undervacuum and the solid was washed with diethyl ether to give thecorresponding hydrochloride salt of the title compound. Afterpurification by ion exchange chromatography, 47 mg (33% yield) of(2SR,1′SR,2′SR,3′RS)-2-(3′-benzylcarbonylaminomethyl-2′-carboxycyclopropyl)glycine wereobtained as a white solid.

³C-NMR (CD₃OD, 50 MHz) δ ppm):177.0, 173.9, 172.4, 135.0, 128.8, 128.7,127.0, 53.8, 42.5, 37.9, 26.6, 26.0, 24.9

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(m-chlorobenzoylaminomethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(azidomethyl)cyclopropyl]glycinate(100 mg, 0.27 mmol) in ethylacetate (4 mL), platinum (IV) oxide (12 mg,0.054 mmol) was added and the mixture was allowed to react at roomtemperature under hydrogen atmosphere for 4 hours. Then, m-chlorobenzoylchloride (0.069 mL, 0.54 mmol) was added and reaction stirred at roomtemperature under nitrogen atmosphere overnight. The following day, themixture was filtered through celite and concentrated under vacuum. Theresidue was purified by column chromatography using hexane and ethylacetate 7:3 as eluent to afford 51 mg (39% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3-(m-chlorobenzoylaminomethyl)-cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ ppm): 7.9 (1H, t, J=1,6 Hz), 7.8-7.7 (2H, dt,J=1,4 Hz, 7,3 Hz), 7.4-7.3 (2H, m), 5.6 (1H, d, J=7,6 Hz), 4.3-4.1 Hz(5H m), 3.1 (2H, ddd, J=3 Hz, 9,9 Hz, 14,6 Hz), 1.9-1.7 (3H, m), 1.4(9H, s), 1.3-1.2 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 171.9, 165.5, 155.5, 136.0, 134.4,131.2, 129.8, 127.4, 125.1, 80.3, 62.2, 60.9, 52.6, 38.2, 28.7, 28.1,26.4, 23.2, 14.0, 13.9

b)(2SR,1′SR,2′SR,3′RS)-2-[3′-(m-chlorobenzoylaminomethyl-2′-carboxycyclopropyl]glycine

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3-(m-chlorobenzoylaminomethyl)cyclopropyl]glycinate(302 mg, 0.63 mmol) in tetrahydrofuran (6.5 mL), a 2.5M solution ofLiOH.H₂O (1.05 g, 25.0 mmol) in H₂O (10 mL) was added and the mixturewas stirred at room temperature overnight. The following day ethylacetate (10 mL) was added, organic layer separated and aqueous layerwashed with ethyl acetate (3×5 mL). The aqueous layer was acidified topH 1 with 1N HCl and extracted with ethyl acetate (5×20 mL). Thecombined organic layers were dried over magnesium sulfate, filtered andconcentrated under vacuum. The residue was dissolved in a 1N solution ofHCl in ethyl acetate (3.5 mL, 3.5 mmol) and the solution was stirredovernight at room temperature. It was concentrated under vacuum and thesolid was washed with diethyl ether to give the correspondinghydrochloride salt of the title compound. After purification by ionexchange chromatography, 97 mg (47% yield) of (2SR,1′SR,2′SR,3′RS)-2-[3-(m-chlorobenzoylaminomethyl)-2′-carboxycyclopropyl]glycinewere obtained as a white solid.

¹³C-NMR (CD₃OD, 50 MHz) δ ppm): 175.1, 170.6, 168.5, 137.3, 135.6,132.7, 131.3, 128.5, 126.7, 53.2, 39.4, 28.1, 27.4, 25.3.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(methylaminomethyl)cyclopropyl]-glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-azidomethylcyclopropyl]glycinate (1.35 mmol, 500 mg) in ethyl acetate (20 mL),platinum (IV) oxide (0.27 mmol, 60 mg) was added and the mixture wasallowed to react at room temperature under a hydrogen atmosphere for 4hours. Then, methyl iodide (2.7 mmol, 0.17 mL) was added and the mixturewas allowed to react under nitrogen at room temperature overnight. Thefollowing day, the mixture was filtered through celite and concentratedunder vacuum. The residue was purified by column chromatography using a4% mixture of methanol in dichloromethane as eluent to afford 380 mg(79% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(methylaminomethyl)cyclopropyl]-glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ ppm): 6.7 (1H, broad s), 5.5 (1H, broad s),4.2-3.9 (5H, m), 3.4-3.0 (2H, m), 2.7 (3H, s), 2.1-1.8 (3H, m), 1.3 (9H,s), 1.2-1.1 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ ppm): 171.8, 171.5, 155.3, 80.3, 62.6, 61.2,52.7, 39.3, 33.3, 28.9, 28.1, 24.7, 24.1, 14.0

b)(2SR,1′SR,2′SR,3′RS)-2-(3′-methylaminomethyl-2′-carboxycyclopropyl)glycine

A solution of ethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[21-(ethoxycarbonyl)-3′-(methylaminomethyl)cyclopropyl]glycinate (188 mg,0.52 mmol) in 2N HCl (5 mL) was stirred at room temperature for 5 days.Then, the solvent was evaporated under reduced pressure and the residuewas dissolved in 6N HCl (2 mL) and allowed to react at room temperaturefor 2 days and at 55° C. for 6 hours. The solvent was then removed undervacuum to afford the corresponding hydrochloride salt of the titlecompound. After purification by ion exchange chromatography, 38 mg (33%yield) of (2SR,1′SR,2′SR,3′RS)-2-[3′-methylaminomethyl-2′-carboxycyclopropyl]glycine wereobtained as a white solid.

¹³C-NMR (D₂O/py-d₅, 50 MHz) δ ppm): 178.5, 172.9, 53.8, 38.3, 31.9,27.0, 25.7, 21.9.

a) Ethyl(2S,1′S,2′R,3′R)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethylcyclopropyl]glycinate

The corresponding enantiomers of ethyl (2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethyl-cyclopropyl]glycinatewere separated by chiral HPLC using the following analytical method:

Chiralpak AD 4.6×250 mm

Eluent: 10% MeOH, 10% IPA in Heptane

Flow: 1.0 mL/min.

UV: 220 nm

Isomer #1 retention time=5.5 min

Isomer #2 retention time=7.0 min

Isomer #2, that was identified as the desired enantiomer, was furtherpurified by silica gel chromatography using EtOAc/hexane (1:1) as theeluent to afford 10.21 g of ethyl(2S,1′S,2′R,3′R)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethylcyclopropyl]glycinate

b) (2S,1′S,2′R,3′R)-2-(3′-hydroxymethyl-2′-carboxycyclopropyl)glycine

To a stirred solution of ethyl(2S,1′S,2′R,3′R)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethyl-cyclopropyl]glycinate(10.21 g, 29.56 mmol, isomer #2 of the separation above) in CH₂Cl₂ (50mL) at 2° C. was added trifluoroacetic acid (22.8 mL, 296 mmol) over afew minutes, maintaining the temperature below 5° C. The mixture wasallowed to warm to room temperature and stirred for 2.5 hours. Then,mixture was evaporated under reduced pressure to give a faint yellowoil. The oil was dissolved in CH₂Cl₂ (35 mL) and the volatilesevaporated (3×). This process was repeated using ethanol (3×40 mL) toafford a faint yellow oil (15.6 g) which was dissolved in 3 N NaOH (49.3mL, 148 mmol) using a water bath to maintain the temperature slightlyabove ambient temperature. The faint yellow homogeneous mixture wasstirred for 1.25 h before the pH was slowly lowered to 3.5 usingconcentrated HCl. Once crystallization initiated, the pH was adjusted to2.55 over 10 min using concentrated HCl. The suspension was cooled to 2°C. and stirred for 2.25 hours before the white solid was collected andwashed with cold water (1×12 mL, 2×5 mL). The material was dried invacuo for several hours at 38° C. and for 2.5 days at room temperature,affording 4.88 g (87% yield) of (2S,1′S,2′R,3′R)-2-(3′-hydroxymethyl-2′-carboxycyclopropyl)glycine.

[α]²⁰ _(D)=+3.3 (c 1.1, 1 N NaOH)

a) Ethyl (1SR,2SR,6RS,7SR)3-(tert-butoxycarbonyl)-4-oxo-3-aza-bicyclo[4.1.0]heptane-2,7-dicarboxylate

To solution of (2SR,1′SR,2′SR,3′RS)N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2′-hydroxyethyl)cyclopropyl]glycinate(1.45 g, 4.48 mmol) in 50 mL of anhydrous CH₂Cl₂, 8.4 g (22.4 mmol) ofPDC (pyridinium dichromate) were added and stirred at room temperaturefor 2 days. Then, 50 mL of CH₂Cl₂ were added, the crude was thenfiltered through celite, and concentrated in vacuo. The residue waspurified by column chromatography using ethyl acetate/hexane 1:1 aseluent to afford 0.48 g (34% yield) of ethyl (1SR,2SR,6RS,7SR)3-(tert-butoxycarbonyl)-4-oxo-3-aza-bicyclo[4.1.0]heptane-2,7-dicarboxylateas a yellow oil.

¹H-NMR (300 MHz, CDCl₃): 1.25 (t, J=7.1 Hz, 3H) 1.30 (t, J=7.1 Hz, 3H),1.49 (s, 9H), 1.73 (t, J=4.1 Hz, 1H), 1.95-1.99 (m, 1H), 2.19-2.25 (m,1H), 2.61 ((dd, J₁=18.0 Hz, J₂=3.2 Hz, 1H), 2.91 ((dd, J₁=18.0 Hz,J₂=6.6 Hz, 1H), 4.13 (q, J=7.1 Hz, 2H), 4.25 (m, 2H), 5.05 (d, J=6.9 Hz,1H) ppm.

¹³C-NMR (75 MHz, CDCl₃): 14.0, 14.1, 19.2, 21.3, 24.0, 27.7, 33.2, 56.7,61.0, 61.8, 84.2, 151.6, 167.7, 169.6, 177.2 ppm.

b) (2SR,1′SR,2′SR,3′RS)2-[2′-carboxy-(3′-carboxymethyl)cyclopropyl]glycine hydrochloride

Ethyl (1SR,2SR,6RS,7SR)3-(tert-butoxycarbonyl)-4-oxo-3-aza-bicyclo[4.1.0]heptane-2,7-dicarboxylatein 6N HCl (4 mL) was refluxed overnight. The following day, solvent wasremoved under vacuo to dryness to afford the corresponding hydrochlorideof(2SR,1′SR,2′SR,3′RS)2-[2′-carboxy-(3′-carboxymethyl)cyclopropyl]glycine.

¹H-NMR (200 MHz, methanol-d₄): 1.61-1.99 (m, 5H), 3.83 (d, 1H)ppm.

¹³C-NMR (50 MHz, methanol-d₄): 22.5, 24.5, 25.4, 31.9, 51.6, 168.8,172.4, 173.7 ppm.

a) trans-4,4,4-Trifluoro-2-buten-1-yl acetoacetate

To a refluxing solution of 4,4,4-trifluoro-2-buten-1-ol (10 g, 79 mmol)and sodium acetate (0.51 g, 6.2 mmol) in anhydrous tetrahydrofuran (27mL) under nitrogen, a solution of diketene (6.7 mL, 43.1 mmol) inanhydrous tetrahydrofuran (14 mL) was added dropwise over a period of 1hour. The reaction mixture was heated at reflux for an additional 30 minupon completion of the addition. Then, the reaction mixture mixture wascooled to room temperature and diluted with diethyl ether (100 mL). Theresulting solution was washed with a saturated aqueous sodium chloridesolution (2×20 mL) and the organic layer was dried over sodium sulfate,filtered and the solvent removed under reduced pressure. The brownresidue was purified by column chromatography using a mixture 4:1 ofhexane and ethyl acetate as eluent to afford 14.0 g (84% yield) oftrans-4,4,4-trifluoro-2-buten-1-yl acetoacetate as a colorless liquid.

¹H-NMR (200 MHz, CDCl₃): 2.25 (s, 3H), 3.51 (s, 2H), 4.78-4.71 (m, 2H),5.97-5.82 (m, 1H), 6.46-6.33 (m, 1H) ppm.

¹³C-NMR (50 MHz, CDCl₃): 30.2, 50.0, 62.1, 115.0, 119.2, 119.9, 120.4,120.6, 121.2, 125.7, 131.1, 133.8, 134.0, 134.1, 134.2, 166.7, and 200.5ppm.

b) trans-4,4,4-trifluoro-2-buten-1-yl diazoacetate

To a solution of trans-4,4,4-trifluoro-2-buten-1-yl acetoacetate (13.7g, 65.1 mmol) and triethylamine (11.7 mL, 84 mmol) in anhydrousacetonitrile (60 mL), a solution of p-acetamidobenzenesulfonyl azide(20.1 g, 84 mmol) in anhydrous acetonitrile (60 mL) was added dropwiseover a period of 30 minutes. A white precipitate was observed after15-20 minutes and additional acetonitrile (100 mL) was added tofacilitate stirring. The resulting mixture was stirred at roomtemperature for one additional hour. Then, a solution of lithiumhydroxyde (9.0 g, 214 mmol) in water (75 mL) was added to the reactionmixture. After stirring for one hour, the resulting mixture was pouredonto 2:1 diethylether:ethyl acetate (150 mL) and layers were separated.Aqueous layer was extracted with 2:1 diethylether:ethyl acetate (150 mL)and the combined organic phases were washed with a saturated aqueoussodium chloride solution (50 mL). The resulting organic solution wasdried over sodium sulfate, filtered and the solvent removed underreduced pressure. The residue was purified by column chromatographyusing a mixture 4:1 of hexane and ethyl acetate as eluent to afford 9.4g (75% yield) of trans-4,4,4-trifluoro-2-buten-1-yl diazoacetate as ayellow oil.

¹H-NMR (200 MHz, CDCl₃): 4.79-4.75 (m, 2H), 4.81 (s, 1H), 5.90-5.75 (m,1H), 6.48-6.36 (m, 1H) ppm.

¹³C-NMR (50 MHz, CDCl₃): 46.6, 62.3, 115.0, 119.2, 119.9, 120.3, 120.6,121.3, 125.7, 131.0 134.3, 134.4, 134.5, 134.6, 166.3 ppm.

c) (1RS,5SR,6RS)-6,6,6-trifluoromethyl-3-oxabicyclo[3.1.0]hexan-2-one

To a solution of Cu(TBS)₂ (1.0 g, 2.4 mmol) in anhydrous toluene (750mL) heated at reflux, a solution of trans-4,4,4-trifluoro-2-buten-1-yldiazoacetate (9.4 g, 48.4 mmol) in anhydrous toluene (750 mL) was addeddropwise over a period of 30 hours. After the addition was complete,mixture was allowed to react under reflux for one hour and then cooledto room temperature. The solvent was removed under reduced pressure andthe residue was purified by column chromatography using hexane and ethylacetate 4:1 as eluent. 4.8 g (60% yield) of (1RS,5SR,6RS)-6,6,6-trifluoromethyl-3-oxabicyclo[3.1.0]hexan-2-one was obtainedas a yellow oil.

¹H-NMR (200 MHz, CDCl₃): 1.95-1.87 (m, 1H), 2.44-2.40 (m, 1H), 2.62-2.54(m, 1H), 4.43-4.37 (m, 2H) ppm.

¹³C-NMR (50 MHz, CDCl₃): 20.1, 20.2, 20.3, 23.6, 24.3, 25.1, 25.8, 68.2,115.4, 120.8, 126.2, 131.6, 172.3 ppm.

d) Methyl(1RS,2SR,3RS)-2-hydroxymethyl-3-trifluoromethylcyclopropropane-1-carboxylate

To a solution of(1RS,5SR,6RS)-6,6,6-trifluoromethyl-3-oxabicyclo[3.1.0]hexan-2-one (4.7g, 28.5 mmol) in tetrahydrofurane (40 mL) at room temperature, asolution of lithium hydroxyde (3.5 g, 83.4 mmol) in water (83 mL) wasadded. The reaction mixture was stirred overnight at room temperatureand the following day the organic phase was removed under vacuo. Theresulting aqueous layer was washed with diethyl ether (2×25 mL) and thencooled to 0° C. After the pH was adjusted to 2-3 by addition of 1N HCl,the aqueous layer was extracted with ethyl acetate (6×100 mL). Thecombined organic phases were dried over sodium sulfate, filtered and thesolvent removed under reduced pressure. The resulting carboxylic acidwas taken into diethyl ether (100 mL) and cooled to 0° C. and a solutionof diazomethane in diethyl ether was added in small portions until TLCshowed no starting material remained. The solvent was then removed underreduced pressure to afford the corresponding methyl(1RS,2SR,3RS)-2-hydroxymethyl-3-trifluoromethylcyclopropropane-1-carboxylate(5.0 g). This crude was used in the next step without furtherpurification.

¹H-NMR (200 MHz, CDCl₃): 2.01-1.87 (m, 1H), 2.34-2.14 (m, 3H),3.75(s,3H), 3.80-3.74 (m, 1H),3.94-3.89 (m, 1H) ppm.

¹³C-NMR (50 MHz, CDCl₃): 20.9, 24.2, 25.0, 25.2, 25.7, 26.5, 52.4, 58.2,116.4, 121.8, 127.2, 132.6, 170.6 ppm.

e) Methyl(1RS,2SR,3RS)-2-formyl-3-trifluoromethylcyclopropropane-1-carboxylate

To a solution of unpurified methyl(1RS,2SR,3RS)-2-hydroxymethyl-3-trifluoromethylcyclopropropane-1-carboxylate(5.0 g, 25.2 mmol) in anhydrous dichloromethane (250 mL) at roomtemperature under nitrogen atmosphere, molecular sieves (4A) (3.8 g) wasadded. After stirring for 15 min, mixture was cooled to 0° C. and asolution of N-methylmorholine-N-oxide (4.42 g, 37.8 mmol) was added.After 10 min, tetrapropylammonium perruthenate (440 mg, 1.26 mmol) wasadded in small portions and the mixture was allowed to react at roomtemperature. The following day, the solvent was removed under vacuo andthe residue was taken into ethyl acetate (200 mL). The resultingsuspension was filtered through a plug of celite and organic layer wasremoved to dryness. After purification of the crude by columnchromatography using ethyl acetate and hexane 1:4 as eluent, 2.1 g (37%yield) of methyl(1RS,2SR,3RS)-2-formyl-3-trifluoromethylcyclopropropane-1-carboxylatewere obtained.

¹H-NMR (200 MHz, CDCl₃): 2.38-2.45 (m, 1H), 2.51-2.59 (m, 1H),2.94-3.03, (m, 1H), 3.76 (s, 3H), 9.40 (d, J=5.1 Hz, 1H) ppm.

¹³C-NMR (50 MHz, CDCl₃): 24.4, 25.2, 26.0, 26.7, 27.5, 30.8, 52.9,120.7, 126.2, 131.6, 167.9, 194.5 ppm.

f) Methyl(1RS,2RS,3RS)-2-formyl-3-trifluoromethylcyclopropropane-1-carboxylate

A solution of sodium hydroxide (10.0 g, 250 mmol) in water (100 mL) wasadded to a solution of methyl (1RS,2SR,3RS)-2-formyl-3-trifluoromethylcyclopropropane-1-carboxylate (1.72g, 8.8 mmol) in methanol (130 mL), and the mixture was stirred at roomtemperature for 4 days. Methanol was then removed under reduced pressureand the resulting aqueous layer was washed with diethyl ether (2×25 mL)and cooled to 0° C. After the pH was adjusted to 3-4 by addition of anaqueous solution of citric acid (10-25%), the aqueous layer wasextracted with ethyl acetate (6×100 mL). The combined organic phaseswere dried over sodium sulfate, filtered and the solvent was removedunder reduced pressure. The resulting carboxylic acid was taken intodiethyl ether (100 mL) and cooled to 0° C., and a solution ofdiazomethane in diethyl ether was added in small portions until TLCshowed no starting material remained. The solvent was removed underreduced pressure and residue purified by column chromatography usinghexane and ethyl acetate 4:1 as eluent to afford 1.25 g (73% yield) ofan inseparable 1:1 mixture of the corresponding methyl(1RS,2RS,3RS)-2-formyl-3-trifluoromethylcyclopropropane-1-carboxylateand starting material. This mixture was used in the next step withoutany other further purification.

¹H-NMR (200 MHz, CDCl₃): 2.62-2.51 (m, 1H), 2.89-2.83, (t, 1H), 3.77 (s,3H), 9.28-9.24 (m, 1H) ppm.

g) (2S,1″R,1′R,2′R,3′R) and (2S,1″R,1′S,2′S,3′S)-N-[(2″-hydroxy-1″-phenyl)ethyl]2-(2′-methoxycarbonyl-3′-trifluoromethylcyclopropyl)glycinonitrile

To a solution of a 1:1 mixture of methyl (1RS,2RS,3RS)-2-formyl-3-trifluoromethylcyclopropropane-1-carboxylate and methyl(1RS,2SR,3RS)-2-formyl-3-trifluoromethyl cyclopropropane-1-carboxylate(1.25 g, 6.3 mmol) in methanol (63 mL), (R)-(−)-2-phenylglycinol (0.96g, 7.0 mmol) was added. The mixture was stirred at room temperature fortwo hours and then cooled to 0° C. Trimethylsilylcyanide (1.66 mL, 12.4mmol) was added to the mixture and allowed to react at room temperatureovernight. The following day the solvent was removed under reducedpressure and residue was purified by column chromatography using ethylacetate and hexane 1:3 as eluent to afford 1.59 g (73% yield) of amixture of four aminonitriles. (2S,1″R,1′R,2′R,3′R) and (2S,1″R,1′S,2′S,3′S)-N-[(2″-hydroxy-1″-phenyl)ethyl]-2-(2′-methoxycarbonyl-3′-trifluoromethylcyclopropyl) glycinonitrile (glycinonitriles A and B) were purified andseparated by column chromatography using dichloromethane and acetone18:1 as eluent.

Glycinonitrile A

¹H-NMR (200 MHz, acetone-d₆): 2.02 (m, 1H), 2.27 (m, 1H), 2.40 (t, 1H),3.06 (d, 1H), 3.60-3.66 (m, 2H), 3.69 (s, 3H), 3.99 (t, 1H), 4.05-4.08(m, 2H), 7.26-7.45 (m, 5H)ppm.

¹³C-NMR (50 MHz, CDCl₃): 22.1, 25.4, 26.2, 26.9, 27.7, 47.4, 52.7, 63.1,66.6, 118.1, 121.8, 127.3, 128.3, 128.7, 139.2, 169.7 ppm.

Glycinonitrile B

¹H-NMR (200 MHz, CDCl₃): 2.09 (t, 1H), 2.15 (m, 1H), 2.32 (m, 1H), 2.59(bs, 1H), 3.24 (d, 1H), 3.74 (s, 3H), 3.79-3.95 (m, 2H), 4.09 (dd, 2H),7.28-7.34 (m, 5H) ppm.

¹³C-NMR (50 MHz, CDCl₃): 21.4, 21.5, 25.4, 26.1, 26.9, 27.0, 46.0, 52.7,63.0, 66.9, 117.9, 121.5, 126.9, 127.7, 128.4, 128.6, 132.3, 136.9,169.9 ppm.

h) (2S,1′R,2′R,3′R) and(2S,1′S,2′S,3′S)-3′-trifluoromethyl-2′-carboxycyclopropylglycinehydrochloride

Lead tetraacetate (35.7 mg, 0.08 mmol) was added to a solution of theglycinonitrile B of step g) (25.1 mg, 0.073 mmol) in a 1:1 mixture ofmethanol and dichloromethane (0.6 mL) at 0° C. After 10 minutes, water(0.3 mL) was added and mixture filtered off through celite. The solventwas removed under reduced pressure and residue was taken into 4N HCl (4mL) and refluxed overnight. The following day, the solvent was removedunder vacuo to dryness to afford the corresponding hydrochloride salt(Aminoacid B).

Aminoacid B

¹H-NMR (200 MHz, methanol-d₄): 3.83 (d, J=14 Hz, 1H), 2.56-2.49 (m, 2H),2.08-2.02 (m, 1H) ppm.

¹³C-NMR (50 MHz, methanol-d4): 22.7, 24.1, 25.4, 25.7, 26.0, 26.3, 63.3,121.9, 124.1, 126.3, 129.2, 168.8, 171.0 ppm.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-benzyloxyethyl)cyclopropyl]glycinate

To a mixture of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(0.84 mmol, 300 mg) and benzyl 2, 2, 2,-trichloroacetimidate (1.01 mmol,0.19 mL) in a 2:1 mixture of cyclohexane and dichloromethane (18 mL) atroom temperature under nitrogen atmosphere, trifluoromethanesulfonicacid (catalytic amount) was added. The mixture was allowed to react atroom temperature for two days and then quenched with water (5 mL). Theaqueous phase was extracted with dichloromethane (2×5 mL) and thecombined organic layers was dried over magnesium sulfate and evaporatedin vacuo. The resulting residue was purified by column chromatographyusing a hexane and ethyl acetate 9:1 as eluent to afford 193 mg (51%yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-benzyloxyethyl)cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 7.3-7.2, (5H, m), 5.3 (1H, broad s), 4.5(2H, s), 4.3-4.0 (5H, m), 3.6-3.5 (2H, m), 2.1 (1H, m), 2.0-1.7 (5H, m),1.4 (9H, s), 1.2-1.1 (6H)

¹³C-NMR (CDCl₃, 200 MHz) δ(ppm): 173.2, 171.3, 157.6, 138.2, 128.3,127.5, 80.1, 72.9, 69.4, 61.6, 60.7, 52.2, 29.6, 28.2, 27.4, 25.1, 24.7,14.1

b)(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-benzyloxyethyl)-2′-carboxycyclopropyl]glycinehydrochloride

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-benzyloxyethyl)cyclopropyl]glycinate(174 mg, 0.39 mmol) in tetrahydrofuran (4 mL), a 2.5M solution ofLiOH.H₂O in H₂O (6.2 mL, 15.5 mmol) was added and the mixture wasstirred at room temperature overnight. The following day, diethyl etherwas added, and organic layer was separated. The aqueous layer was washedwith diethylether (3×3 mL). The aqueous layer was acidified to pH 1 with1N HCl and extracted in diethyl ether (5×5 mL). The combined organiclayers were dried over magnesium sulfate, filtered and concentratedunder vacuum. The residue was dissolved in a 1N solution of HCl in ethylacetate (8 mL, 80 mmol) and the solution was stirred overnight at roomtemperature. It was concentrated under vacuum and the solid was washedwith Et₂O to give 25 mg (19% yield) of the title compound.

¹³C-NMR (CDCl₃, 200 MHz) δ(ppm): 174.9, 169.6, 137.7, 128.1, 127.5,72.5, 68.8, 51.8, 27.6, 26.0, 25.1, 24.7

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-diphenylphosphoryloxyethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(100 mg, 0.28 mmol) in anhydrous toluene (2 mL) at room temperatureunder nitrogen atmosphere, diphenylphosphorylazide (0.053 mL, 0.33 mmol)was added. After 30 minutes, DBU was added (0.046 mL, 0.31 mmol) and thereaction mixture stirred overnight. The following day reaction mixturewas quenched with water (2 mL) and aqueous phase extracted with ethylacetate (2×2 mL). The combined organic layers were dried over magnesiumsulfate, filtrated and evaporated under reduced pressure. The resultingresidue was purified by column chromatography using hexane and ethylacetate 7:3 as eluent to afford 132 mg (80% yield) of ethyl (2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-diphenylphosphoryloxyethyl)cyclopropyl]glycinate

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 7.4-7.2 (1OH, m), 5.2 (1H, broad s), 4.3(2H, q, J=7 Hz), 4.2 (2H, q, J=7.2 Hz), 4.0 (2 H, dd, J=1,8 Hz, 7 Hz),2.3-2.1 (1H, m), 1.8-1.6 (4H, m), 1.4 (9H, s), 1.2 (3H, t, J=7,2 Hz),1.1 (3H, t, J=7,2 Hz)

¹³C-NMR (CDCl₃, 200 MHz) δ(ppm): 173.9, 172.4, 151.4, 129.7, 125.2,120.0, 119.9, 80.7, 68.2, 61.7, 60.7, 52.1, 29.5, 28.8, 28.1, 24.5,23.7, 14.0

b) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-azidoethyl)cyclopropyl]glycinate

A solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-diphenylphosphoryloxyethyl)cyclopropyl]glycinate(445 mg, 0.75 mmol) and sodium azide (98 mg, 1.5 mmol) in anhydrousdimethylformamide (7 mL) was stirred at room temperature for two daysand then heated at 60° overnight. Then, the reaction was quenched withwater (10 mL) and the aqueous phase was extracted with ethyl acetate(3×5 mL). The combined organic layers were washed with water (6×5 mL).The organic layer was dried over magnesium sulfate and the solventevaporated in vacuo. The resulting residue was purified by columncromatography using hexane and ethyl acetate 8:2 as eluent to afford 216mg (75% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-azidoethyl)cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 5.2 (1H, broad s), 4.2 (2H, q, J=7,2Hz), 4.1 (2H, q, J=7.2 Hz), 3.9 (1H, m), 3.4 (2H, t, J=6, 6 Hz), 2.0(1H, m), 1.7-1.6 (3H, m), 1.4 (9H, s), 1.3 (3H, t, J=7,2 Hz), 1.2 (3H,t, J=7,2 Hz)

¹³C-NMR (CDCl₃, 200 MHz) δ(ppm): 172.5, 170.9, 153.9,79.9, 61.5, 60.6,52.0, 50.7, 29.5, 28.0, 27.5, 24.8, 13.9

c) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-nitroethyl)cyclopropyl]-glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-azidoethyl)cyclopropyl]glycinate (167 mg, 0.43 mmol) in ethyl acetate (4 mL),platinum (IV) oxide was added (19.5 mg, 0.086 mmol) and the mixtureallowed to react at room temperature under a hydrogen atmosphere for 4hours. Then, mixture was filtered through celite and concentratedevaporated to dryness. The resulting residue was disolved indichloromethane (4 mL), cooled to 0° C. and treated in one portion with80% 3-chloroperoxybenzoic acid (223 mg, 1.29 mmol) and stirred at roomtemperature overnight. The following day, 2-propanol was added to thereaction mixture and then poured into a 1:1 mixture of a saturatedaqueous solution of sodium bicarbonate and ethyl acetate (10 mL). Theaqueous layer was extracted with ethyl acetate (3×10 mL), and thecombined organic layers washed with brine and dried over sodium sulfate.The solvent was evaporated under vacuo, and the resulting residue waspurified by column chromatography using hexane and ethyl acetate 9:1 aseluent to afford 20 mg (12% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-nitroethyl)-cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 4.6 (2H, t, J=6,9 Hz), 4.5-4.0 (5H, m),2.4-2.0 (1H, m), 1.8-1.6 (4H, m), 1.4 (9H, s), 1.3 (3H, t, J=7,2 Hz),1.2 (3H, t, J=7,2 Hz)

¹³C-NMR (CDCl₃, 200 MHz) δ(ppm): 170.8, 170.0, 155.2, 80.4, 74.4, 62.0,61.0, 51.8, 29.8, 28.1, 25.8, 24.3, 23.9, 14.0

d)(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-nitroethyl)-2′-carboxycyclopropyl]glycinehydrochloride

A 2.5M solution of LiOH.H₂O in H₂O (1.5 mL, 3.6 mmol) was added to asolution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-nitroethyl)cyclopropyl]glycinate(24.0 mg, 0.06 mmol) in THF (1 mL) and the mixture was stirred at roomtemperature overnight. Et₂O was added (1 mL), the organic layer wasseparated and the aqueous layer was washed with Et₂O (3×1 mL). Theaqueous layer was acidified to pH 1 with 1N HCl and extracted in Et₂O(5×2 mL). The combined organic layers were dried over MgSO₄, filteredand concentrated under vacuum. The residue was dissolved in a 2Msolution of HCl in Et₂O (4 mL/mmol) and the solution was stirredovernight at room temperature. The mixture was concentrated under vacuumand the solid was washed with Et₂O to give 3 mg (16% yield) of the titlecompound.

¹³C-NMR (CDCl₃, 200 MHz) δ(ppm): 173.3, 166.7, 74.1, 51.6, 29.2, 25.3,24.4, 23.9

a)(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-azidoethyl)-2′-carboxycyclopropyl]glycinehydrochloride

A 2.5M solution of LiOH.H₂O in H₂O (7.7 mL, 19.2 mL) was added to asolution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-azidoethyl)cyclopropyl]glycinate(185 mg, 0.48 mmol) in THF (5 mL) and the mixture was stirred at roomtemperature overnight. Et₂O was added (5 mL), the organic layer wasseparated and the aqueous layer was washed with Et₂O (3×5 mL). Theaqueous layer was acidified to pH 1 with 1N HCl and extracted in Et₂O(5×10 mL). The combined organic layers were dried over MgSO₄, filteredand concentrated under vacuum. The residue was dissolved in a 2Msolution of HCl in Et₂O (4 mL) and the solution was stirred overnight atroom temperature. The mixture was concentrated under vacuum and thesolid was washed with Et₂O to afford 117 mg (90% yield) of the titlecompound.

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 3.81 (1H, d, J=10,4 Hz), 3.4 (2H, t,J=6,9 Hz), 2.1 (1H, m), 1.9-1.5 (5H, m).

¹³C-NMR (CDCl₃, 200 MHz) δ(ppm): 173.9, 169.1, 51.7, 50.5, 27.0, 26.0,25.0, 24.6.

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-p-toluensulfonyloxyethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2-(ethoxycarbonyl)-3′-(2″-hydroxyethyl)cyclopropyl]glycinate(200 mg, 0.56 mmol) in pyridine (10 mL) two equivalents ofp-toluenesulfonyl chloride (0.21 g, 1.11 mmol) were added at roomtemperature and the reaction was stirred for 40 hours. Then, H₂O andEtOAc were added and the organic layer was separated. The aqueous layerwas extracted with EtOAc (3×) and the combined organic layers werewashed with H₂O (5×), dried over MgSO₄, filtered and concentrated undervacuum. The residue was purified by column chromatography using a 2:1mixture of hexane/EtOAc as eluent to afford 110 mg (38% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-p-toluensulfonyloxyethyl)-cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 7.7 (2H, d, J=8 Hz), 7.2 (2H, d, J=8Hz), 5.5 (1H, d, J=8 Hz), 4.2-3.7 (7H, m), 2.3 (1H, s), 2.2-1.5 (5H, m),1.5 (9H, s), 1.3-1.1 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ(ppm): 172.4, 170.9, 155.3, 144.7, 132.8,129.8, 127.8, 80.0, 69.2, 61.7, 60.7, 52.0, 29.5, 28.1, 27.6, 24.4,23.6, 21.5, 14.0

b) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-cyanoethyl)cyclopropyl]glycinate

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-p-toluensulfonyloxyethyl)cyclopropyl]glycinate(500 mg, 0.97 mmol) in DMSO (10 mL) five equivalents of potassiumcyanide (0.31 g, 4.85 mmol) were added at room temperature and thereaction was stirred for 5 days. Then, H₂O and EtOAc were added and theorganic layer separated. The aqueous layer was extracted with EtOAc (3×)and the combined organic layers were washed with H₂O (5×), dried overMgSO₄, filtered and concentrated under vacuum. The residue was purifiedby column chromatography using a 2:1 mixture of hexane/EtOAc as eluentto afford 180 mg (50% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-cyanoethyl)cyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 5.3 (1H, d, J=8 Hz), 4.2-3.8 (5H, m),2.5 (2H, t, J=7 Hz), 2.3-1.5 (5H, m), 1.4 (9H, s), 1.3-1.1 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ(ppm): 172.4, 170.9, 155.3, 118.9, 80.2, 61.6,60.9, 52.0, 29.9, 28.1, 26.1, 24.5, 24.2, 16.9, 14.0

c)(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-carboxyethyl)-2′-carboxycyclopropyl]glycinehydrochloride (3)

A solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-cyanoethyl)cyclopropyl]glycinate (50 mg, 0.14 mmol) in 1N HCl (4 mL) was refluxed overnight.The residue was concentrated under vacuum, washed with EtOAc and driedunder vacuum giving rise to 40 mg (68% yield) of the title compound.

¹H-NMR (D₂O, 200 MHz) δ(ppm): 3.8 (1H, d, J=11 Hz), 2.7-1.5 (7H, m)

¹³C-NMR (D₂O/MeOH-d₄, 50 MHz) δ(ppm): 178.7, 177.2, 171.5, 53.2, 34.2,28.5, 27.7, 26.0, 23.9

a)(2SR,1′SR,2′SR,3′RS)-2-[3′-(2″-(1H-tetrazol-5-yl)-ethyl)-2′-carboxycyclopropyl]glycinehydrochloride

To a solution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(2″-cyanoethyl)cyclopropyl]glycinate(50 mg, 0.14 mmol) in toluene (0.3 mL), two equivalents of tributyltinazide (0.28 mmol, 92 mg) were added under nitrogen at room temperatureand the mixture was heated at 60 C. for 3 days. After cooling down, 1NHCl (4 mL) was added and the resulting reaction mixture was refluxedovernight. After cooling down, EtOAc was added and the organic layer wasseparated. The aqueous layer was washed with EtOAc (3×) and thenconcentrated under vacuum. The solid residue was washed with diethylether and dried under vacuum giving rise to 36 mg (64% yield) of thetitle compound.

¹H-NMR (D₂O/MeOH-d₄, 200 MHz) δ(ppm): 3.7 (2H, d, J=11 Hz), 3.0 (2H, m),2.3-1.4 (5H, m)

¹³C-NMR (D₂O/MeOH-d₄, 50 MHz) δ(ppm): 176.5, 171.2, 157.3, 53.2, 28.1,27.4, 26.6, 26.2, 23.4

a) Ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(5-phenyltetrazol-2-yl)-methylcyclopropyl]glycinate

Diethyl azodicarboxylate (2.16 mmol, 0.34 mL) was added to a solution oftriphenylphosphine (2.16 mmol, 0.57 g) in anhydrous THF (40 mL) undernitrogen at room temperature. Then, a solution of ethyl (2SR,1′SR,2′RS,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-hydroxymethyl-cyclopropyl]glycinate(1.74 mmol, 600 mg) in THF (10 mL) and 5-phenyl-1H-tetrazole (1.13 mmol,0.15 g) were subsequently added and the reaction mixture stirred for 7days at room temperature. The reaction mixture was quenched with water,extracted with EtOAc, and the combined organic layers were dried overmagnesium sulfate, filtered and concentrated under vacuum. The residuewas purified by column chromatography using a 2:1 mixture ofhexane/EtOAc as eluent to afford 500 mg (61% yield) of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(5-phenyltetrazol-2-yl)methylcyclopropyl]glycinate.

¹H-NMR (CDCl₃, 200 MHz) δ(ppm): 8.1 (2H, m), 7.4 (3H, m), 5.6 (1H, d,J=8 Hz), 5.1 (1H, dd, J=6, 14 Hz), 4.7 (1H, dd, J=8,14 Hz), 4.3-3.9 (5H,m), 2.3-1.9 (3H, m), 1.4 (9H, s), 1.2-1.1 (6H, m)

¹³C-NMR (CDCl₃, 50 MHz) δ(ppm): 171.5, 170.5, 165.0, 155.3, 130.2,128.3, 127.3, 126.7, 80.2, 61.7, 60.9, 51.7, 29.4, 28.1, 25.1, 24.3,13.9

b)(2SR,1′SR,2′SR,3′RS)-2-[3′-(5-phenyl-tetrazol-2-yl)methyl-2′-carboxycyclopropyl]glycine

A 2.5M solution of LiOH.H₂O in H₂O (16.8 mL, 42 mmol) was added to asolution of ethyl(2SR,1′SR,2′SR,3′RS)-N-(tert-butoxycarbonyl)-2-[2′-(ethoxycarbonyl)-3′-(5-phenyltetrazol2-yl)methylcyclopropyl]glycinate(0.5 g, 1.05 mmol) in THF (10 mL) and the mixture was stirred at roomtemperature overnight. EtOAc was added, the organic layer was separatedand the aqueous layer was washed with EtOAc (3×). The aqueous layer wasacidified to pH 1 with 1N HCl and extracted in EtOAc (5×). The combinedorganic layers were dried over MgSO₄, filtered and concentrated undervacuum. The residue was dissolved in a 1N solution of HCl in EtOAc (8mL) and the solution was stirred overnight at room temperature. It wasconcentrated under vacuum and the solid was washed with Et₂O. The finalaminoacid was isolated by ion exchange chromatography (150 mg, 50%yield).

¹H-NMR (D₂O/Py-d₅, 200 MHz) δ(ppm): 7.5 (2H, m), 7.0 (3H, m), 5.1 (1H,dd, J=6, 14 Hz), 4.3 (1H, dd, J=10, 14 Hz), 3.5 (1H, d, J=10 Hz),2.1-1.8 (3H, m)

¹³C-NMR (D₂O/Py-d₅, 50 MHz) δ(ppm): 178.4, 172.9, 164.5, 130.8, 129.1,126.7, 126.2, 54.9, 53.2, 28.5, 26.5, 24.5

What is claimed is:
 1. A compound of the formula:

in which R¹ is halo-C₁₋₁₀ alkyl; halo-C₂₋₁₀ alkenyl; or (CH₂)_(n)Y inwhich n is 1 or 2 and Y is OH, CN, N₃, SH, S(O)_(p)R⁴, S(O)₃H, NH₂,NHR⁵, NR⁶R⁷, NHCOR⁸, NO₂, CO₂H, CONHR⁹, 1H-tetrazol-5-yl,5-phenyltetrazol-2-yl, or PO₃H₂; R³, R⁵, R⁶, R⁷, R⁸ and R⁹ are eachselected independently from C₁₋₄ alkyl, aryl and aryl-C₁₋₄ alkyl; R⁴ isselected from C₁₋₄ alkyl, aryl, aryl-C₁₋₄ alkyl, 1H-tetrazol-5-yl,carboxy-C₁₋₄ alkyl and 1H-tetrazol-5-yl-C₁₋₄ alkyl; and p is 0, 1, 2 or3; or a salt or ester thereof.
 2. A compound as claimed in claim 1 ofthe configuration


3. A compound as claimed in claim 1 of the configuration


4. A compound according to any one of claims 1 to 3, in which R⁴ isselected from C₁₋₄ alkyl, aryl, aryl-C₁₋₄ alkyl, and1H-tetrazol-5-yl-C₁₋₄ alkyl.
 5. A compound according to any one ofclaims 1 to 3, in which R¹ is selected from fluoromethyl,trifluoromethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, chloromethyl,2-chloroethyl, trichloromethyl, and 2,2,2-trichloroethyl, 2-fluorovinyl,2,2-difluorovinyl, hydroxymethyl, 2-hydroxyethyl, cyanomethyl,2-cyanoethyl, azidomethyl, 2-azidoethyl, mercaptomethyl,2-mercaptoethyl, methanethiomethyl, 2-methanethioethyl,1H-tetrazol-5-ylthiomethyl, carboxymethylthiomethyl, phenylthiomethyl,methanesulfinylmethyl, 2-methanesulfinylethyl, methanesulfonylmethyl,phenylsulfinylmethyl, phenylsulfonylmethyl, 2-methanesulfonylethyl,2-phenylthioethyl, 2-benzylthioethyl, aminomethyl, acetylaminomethyl,benzoylaminomethyl, 3-chlorobenzoylaminomethyl,benzylcarbonylaminomethyl, methylaminomethyl, nitromethyl, 2-nitroethyl,1H-tetrazol-5-ylmethyl, 2-(1H-tetrazol-5-yl)ethyl,5-phenyltetrazol-2-ylmethyl, carboxymethyl, 2-carboxyethyl,aminocarbonylmethyl, phosphonomethyl, acetamidomethyl, benzamidomethyl,and 2-benzamidoethyl.
 6. A compound according to claim 4, in which R¹ isselected from fluoromethyl, 2-fluoroethyl, trifluoromethyl,trichloromethyl, trichloroethyl, 2-trichloroethyl, 2-fluorovinyl,2,2-difluorovinyl, hydroxymethyl, cyanomethyl, 2-cyanoethyl,azidomethyl, 2-azidoethyl, mercaptomethyl, methanethiomethyl,2-methanethioethyl, 1H-tetrazol-5-ylthiomethyl, methanesulfinylmethyl,2-methanesulfinylethyl, methanesulfonylmethyl, 2-methanesulfonylethyl,aminomethyl, acetylaminomethyl, nitromethyl, 1H-tetrazol-5-ylmethyl,carboxymethyl, 2-carboxyethyl, methylcarboxamide, phosphonomethyl,acetamidomethyl and benzamidomethyl.
 7. A compound according to claim 6,in which R¹ is hydroxymethyl.
 8. A compound according to claim 1, whichis selected from:(2SR,1′SR,2′RS,3′RS)-2-(3′-hydroxymethyl-2′-carboxycyclopropyl)glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-hydroxyethyl)-2′-carboxy)cyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-mercaptomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-carboxymethylthiomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-(1H-tetrazol-5-ylthiomethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[(3′-(2″-mercaptoethyl)-2′-carboxy)cyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-methylthiomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-phenylthiomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-phenylthioethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-benzylthioethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-methylsulfonylmethyl-2′-carboxycyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-phenylsulfonylmethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-azidomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2′-fluoroethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-chloroethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-acetylaminomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-benzoylaminomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-aminomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-benzylcarbonylaminomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-(m-chlorobenzoyl)aminomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-methylaminomethyl-2′-carboxycyclopropyl]glycine;(2SR,1′RS,2′RS,3′RS)-2-[3′-trifluoromethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-carboxymethyl-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-(1H-tetrazol-5-yl)ethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-carboxyethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-azidoethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[(3′-(2″-nitroethyl)-2′-carboxycyclopropyl]glycine;(2SR,1′SR,2′SR,3′RS)-2-[3′-(5-phenyltetrazol-2-yl)methyl-2′-carboxycyclopropyl]glycine,and pharmaceutically acceptable salts and esters thereof. 9.(2S,1′S,2′R,3′R)-2-(3′-hydroxymethyl-2′-carboxycyclopropyl)glycine, or apharmaceutically acceptable salt thereof.
 10. A pharmaceuticalformulation comprising a compound of formula I as claimed in any one ofclaims 1 to 3, 8 or 9, or a pharmaceutically acceptable metabolicallylabile ester thereof, or a pharmaceutically acceptable salt thereof,together with a pharmaceutically acceptable carrier, diluent orexcipient.
 11. A process for preparing a compound of formula I asclaimed in any one of claims 1 to 3, 8 or 9, or a salt or ester thereof,which comprises: (a) deprotecting a compound of formula

in which R¹⁰ and R¹¹ each independently represents hydrogen or acarboxyl protecting group, and R¹² represents hydrogen or an amineprotecting group; (b) hydrolysing a compound of formula

in which R¹³ represents a hydrogen atom or a carboxyl protecting group,and R¹⁴ and R¹⁵ each independently represents a hydrogen atom, a C₁₋₄alkyl group or a phenyl C₁₋₄ alkyl group in which the phenyl group isunsubstituted or substituted by halo, C₁₋₄ alkyl, C₁₋₄ alkoxy or C₃₋₄alkenyl; or (c) hydrolysing a compound of formula

in which R¹⁶ represents a hydrogen atom or a carboxy protecting group,and R¹⁷ represents a hydrogen atom or an amine protecting group;followed when necessary by recovering a diastereomer or isomer of thecompound, or forming a salt or ester thereof.
 12. A method of treating apatient suffering from or susceptible to a disorder of the centralnervous system, which comprises administering an effective amount of acompound of formula I according to claim 1, or a pharmaceuticallyacceptable metabolically labile ester thereof, or a pharmaceuticallyacceptable salt thereof.